The Changing Cleavage Politics of Western Europe

How are the contours of Western European politics shifting? To what extent do these shifts reflect changes in the underlying social and economic structure of European polities? In this article,we reflect on insights from the classic literature on how cleavages structure party systems and consider how the emergence and persistence of new parties and new ideological conflicts are leading to both shifts of dividing lines of party competition and the fragmentation of party systems.While increasing attention has been given to the so-called second dimension of European electoral politics, we highlight the relatively limited focus on structural changes that are helping to drive this transformation. We identify some socio-demographic developments that are potentially generating new cleavages in Western European democracies: the expansion of higher education; mass migration and the growing ethnic diversity of electorates; the aging of societies and sharpening of generational divides; and increased geographical segregation of populations between prospering, globalized major cities and declining hinterlands.


INTRODUCTION
Across Western Europe, democratic politics is experiencing a period of disruption and fragmentation-reflecting and reinforcing the decline in traditional lines of political conflict. New parties have achieved unprecedented success in many mature European democracies, while many traditional governing parties of the center left and center right have hit record lows. How are the contours of Western European politics shifting? To what extent do these shifts reflect changes in the underlying social and economic structure of European polities? What new cleavages are emerging that disrupt the traditionally dominant dimensions of electoral politics, threatening to render old patterns of competition obsolete and realigning politics around new ideological conflicts? While it is tempting to focus on the short-term forces shaping the twists and turns of European politics, there is much to be gained from stepping back to take a long view of how the structural divisions that shape electoral politics have changed and continue to change.
In this review, we first reflect on the insights of the classic literature on how cleavages structure party systems-and the subsequent observation that those traditional cleavages are in long-term decline via changing class structures, secularization, and postmaterialist values underpinned by rising prosperity. We then consider how the emergence and persistence of new parties (notably the radical right, greens, and liberals) and new ideological conflicts (which have been described variously as open-closed, liberal-authoritarian, cosmopolitan-parochial, cosmopolitan-communitarian, cosmopolitan-nationalist, etc.) are leading to both shifts of the dividing lines of party competition and fragmentation of party systems-as the traditional left-right dimension comes under strain. While increasing scholarly attention has been given to this emerging second dimension of European politics, in particular to the strategic behavior of political parties in response to new pressures driven by globalization and European integration, there has been less focus on the shifts in the composition of European electorates that are helping to drive electoral change.
In this review, we identify socio-demographic developments that are potentially generating new cleavages in Western European democracies. These include the expansion of higher education and rise of a mass graduate class; the corresponding decline of school leavers with few or no educational qualifications; mass migration and the growing ethnic diversity of electorates; the aging of societies and sharpening of generational divides; and increased geographical segregation of populations between prospering, globalized major cities and declining hinterlands. These trends, we argue, are setting the scene for a transformation of the dominant electoral cleavages of Western European politics. Having outlined the ways in which these developments might influence the lines of ideological and party conflict, we conclude by reflecting on the broader processes underlying social and economic change in advanced industrial countries.

THE RISE AND FALL OF THE CLASSIC CLEAVAGE MODEL
In their classic account of the formation of party systems in Western Europe, Lipset & Rokkan (1967) argued that long-standing social conflicts predating the emergence of the mass franchise helped to structure political competition once universal suffrage was introduced in Europe. Specifically, processes of nation building and industrialization had generated four major divides, or cleavages, which structured subsequent political conflict: center-periphery (territorial), religioussecular (church versus state), urban-rural, and labor-capital. The "National Revolution" (Lipset & Rokkan 1967) led to a center-periphery conflict between the national culture and subordinate ethnic, linguistic, and religious groups, often located in peripheral areas. It also led to churchstate tension, as the state grew and the church sought to protect its historic powers. Following this, the Industrial Revolution first gave rise to an urban-rural conflict between the traditional landed elite and new bourgeois industrialist class, and subsequently to conflict between workers and capitalists-underpinning the development of the labor movement and left parties.
The configuration of party systems in different European societies reflected the different mix of social conflicts that were salient at the outset of mass democracy. For example, in Austria, the dominant parties of the postwar era were the Austrian People's Party (ÖVP, a successor to the Christian Social Party) and the Social Democratic Party (SPÖ)-reflecting the persisting influence of the church-state conflict and the labor-capital conflict, respectively. In contrast, the Belgian party system has been more heavily structured by a center-periphery conflict-reflecting ethnolinguistic divisions between the regions of Flanders and Wallonia-combined with the church-state conflict (via Francophone and Walloon Christian Democrat parties) and the labor-capital conflict (between social democratic parties on the one hand and liberal conservative parties on the other). In Nordic countries, the power of landed rural interests increased the salience of the urban-rural conflict, expressed through the lasting influence of agrarian parties (such as Venstre in Denmark and the Centre Party in Sweden).
Political parties, Lipset & Rokkan (1967) argued, played a critical role in stabilizing and institutionalizing patterns of competition-developing organizational structures and forging long-term partisan commitments among core supporters. These structures and commitments enabled parties to consistently mobilize their core constituencies and to fend off the emergence of new challengers, thus "freezing" the cleavages structuring party competition. Consequently, Lipset & Rokkan observed, the party system present in most Western European countries in the 1960s continued to reflect much earlier social conflicts-typically conflicts that were salient when the mass franchise first arrived, long after they had weakened or faded from view in the broader society. Lipset & Rokkan (1967) did not offer a clear definition of political cleavages, but subsequent researchers have advanced a three-part formula. The first is social-structural-cleavages exist between large social groups with conflicting interests. The second is psychological-cleavages involve the perception of distinct group identities, ideological values, and interests among group members. The third is organizational-the mobilization of these identities, loyalties, and values by political parties, who then structure and institutionalize the political conflicts arising between groups (Bartolini & Mair 1990, p. 215). All cleavage politics is therefore, at least in part, identity politics, since stable cleavages depend on groups with stable and shared identities that are organized into politics by parties. A crucial set of observations by Lipset & Rokkan (1967, p. 6) was that only a few salient conflicts would polarize a political system, that some cleavages would prove more important than others, and that these cleavage structures would "also tend to undergo changes over time." The subsequent debate over cleavages has tended to focus on two issues. First is whether the traditional social cleavages, particularly those of religion and class, have declined due to social changes such as secularization and the decline of traditional industries (e.g., Przeworski 1985, Norris & Inglehart 2004). These changes have shrunk the social groups in which religious and working-class parties were originally based, stimulating a great deal of research debating the relative impact of changing group sizes, changing behavior within groups, and changing party appeals to groups on the patterns of class and religious voting (Evans 2000, Knutsen 2006, Evans & Tilley 2018. While most researchers agree that there has been some decline in class and religious voting, there are intense debates over whether class and religion are dead as political cleavages, and, if so, who killed them (e.g., Elff 2007, van der Brug 2010, Best 2011, Elff & Rossteutscher 2011, van der Meer et al. 2012, Evans & De Graaf 2013, Heath 2015.
Alongside the question of declines (or not) in traditional cleavages is the second, more general question of whether the cleavage politics model of stable, socially structured party competition is in decline (Franklin 1992). There is much discussion of whether frozen party systems have thawed as more educated and politically engaged voters no longer align in stable and predictable ways with social groups or political parties. "Catch-all" parties without stable social bases (Katz & Mair 1995) now compete in a more volatile electoral market (Pedersen 1979, Fieldhouse et al. 2019, where the fortunes of parties can change rapidly in response to shifts in voters' issue preferences and priorities (Bélanger & Meguid 2008, Green-Pedersen 2019, in response to perceptions of the competence of parties and their leaders (Clarke et al. 2004, Green & Jennings 2017, or in response to the rise and fall of the economic cycle (Lewis-Beck & Stegmaier 2000, Duch & Stevenson 2008. But there is another possibility, raised by Lipset & Rokkan's (1967) original analysis but neglected by many of the researchers focused on freezing and thawing-that cleavage structures could change organically, with new divides emerging as others fade away. A decline of traditional cleavages need not produce an open, unstructured politics but could instead result in the reorganization of party competition around new structural cleavages, as new divides open up in society and are mobilized and organized either by new parties or by major realignments in the support of existing parties.

A SECOND DIMENSION OF POLITICAL CONFLICT?
While lively debate has continued over whether traditional economic and religious cleavages have declined, disappeared, or endured in new forms, a separate literature puts forward a very different account of social and political change-one focused less on the fate of traditional cleavages and more on the emergence of a new dimension of political conflict cutting across the old divisions and restructuring the basis of political competition. Three accounts of this process have been particularly influential-each proposing a different basis for this second dimension: "materialists" versus "postmaterialists" (Inglehart 1977(Inglehart , 1990(Inglehart , 1997; the "winners" and "losers" of globalization (Kriesi et al. 2008(Kriesi et al. , 2012; and a conflict over "transnational" political integration between "Green-Alternative-Liberal" and "Traditional-Authoritarian-Nationalist" voters and parties (Hooghe & Marks 2009. Inglehart's (1977Inglehart's ( , 1990Inglehart's ( , 1997Inglehart's ( , 2008 postmaterialism thesis involves two interlocking mechanisms. First, the "hierarchy of needs" (Maslow 1943) organizes human goals by urgency. When resources are scarce, basic material needs such as food, shelter, and security take precedence, but once growing prosperity enables society to meet such needs, citizens turn to more abstract, longterm goals such as personal freedom and self-expression. The second mechanism is socializationvoters' values and political priorities are formed early in adulthood and remain relatively fixed thereafter. Combining the two produces Inglehart's "silent revolution": The mix of values in society changed as the materialist generations who grew up with the war, want, and insecurity of the first half of the twentieth century died off and were replaced by postmaterialist generations who were socialized into postwar prosperity. Yet generational replacement is very slow, so the process involves many decades of two-dimensional political conflict, with material and postmaterial values both playing important roles.
The influential studies of colleagues (2008, 2012) also propose the emergence of a second dimension of political competition but develop a different account of its emergence. Kriesi et al. (2006) see globalization as the critical process driving the emergence of a new cleavage, generating a conflict between globalization winners (social groups who benefit from and embrace economic integration) and losers (those groups who gain little from globalization, which exposes them to many new economic risks). The groups identified as winners and losers in their analysis are heterogeneous and somewhat vaguely defined. On the winning side, for example, are those with high levels of transferable skills (in practice defined usually as university graduates) and "all kinds of cosmopolitan citizens"; the losers include those with few or no formal qualifications, "employees in traditionally protected sectors," and "citizens who strongly identify themselves with their national community" (Kriesi et al. 2006, p. 922). This globalization cleavage is emerging in all mature democracies, but in keeping with the Lipset & Rokkan (1967) tradition, Kriesi and colleagues focus on how the political expression of globalization divisions is critically shaped by the existing party system and political culture of each national context. Although the cleavage is transnational, its expression can only be understood in national terms.
Does the new globalization cleavage drive party system change, or do existing parties adjust themselves to incorporate it into existing patterns of competition? Kriesi et al. (2006Kriesi et al. ( , 2008Kriesi et al. ( , 2012 are ambiguous on this question. They emphasize the flexibility and adaptability of traditional parties yet also highlight that many such parties have failed to take clear positions on the new dimension or cannot do so because it divides them internally. Therefore, Kriesi and colleagues suggest, much of the mobilization on the new dimension occurs via the emergence of new parties, in particular new radical right parties mobilizing the losers' side of the new globalization cleavage. This emphasis on the emergence of a distinctive new party family seems at odds with their additional claim that the new divides of globalization do not represent a new dimension of political competition but instead a reconfiguration of an already long-established second dimension. In addition, Kriesi et al.'s emphasis on radical right parties as the principal drivers of party system change seems increasingly at odds with contemporary developments, particularly since the global financial crisis, with the emergence of a cluster of electorally significant green and liberal parties that draw their support primarily from groups on the winners' side of the globalization cleavage. Hooghe & Marks (2009 have also proposed a single second dimension of politics, which they call the transnational or GAL-TAN (Green-Alternative-Liberal versus Traditional-Authoritarian-Nationalist) cleavage. The economic and political integration and mobility across borders associated with the development of the European Union in the past few decades, in their view, constitute a "critical juncture" akin to those identified by Lipset & Rokkan (1967) as fundamental to the formation of party system cleavages. To Lipset & Rokkan's National and Industrial Revolutions we now need to add a divide over the contemporary "European Revolution." Like the earlier revolutions, this new wave of political and social change has polarized societies between those who embrace changes that fit their values or serve their interests (the highly educated, the young, migrants, and residents of globally integrated big cities) and those who resist changes they see as threatening to traditional identities and economic security (the low-skilled, the old, cultural and national traditionalists, and residents of struggling hinterland regions).
There are substantial differences in these approaches. Inglehart (1977Inglehart ( , 1990Inglehart ( , 1997 grounds his postmaterialism hypothesis in comparative cross-sectional survey indicators that track evolving value orientations over many decades. However, critical reappraisals have raised issues with these measures and their interpretation (Clarke et al. 1999, Duch & Taylor 1993, suggesting that it may not be economic conditions during socialization that drive the rise of postmaterialism but instead other structural changes such as rising access to higher education among younger generations. Inglehart and his collaborators have also tended to focus largely on mapping the value changes in society, and have had much less to say about how these are organized into political competition by parties. The more recent accounts of Kriesi et al. (2008Kriesi et al. ( , 2012 and Hooghe & Marks (2009) exhibit the opposite mix of strengths and weaknesses. Both focus on the organizational aspect of the second dimension, typically operationalizing that dimension in terms of the issues that parties emphasize and talk about. This approach provides systematic evidence on how party systems are reorienting their appeals around new ideological divides, but it gives us little direct evidence on the changes within the electorate that are stimulating these shifts. It is not clear, for example, whether the emergence of new second-dimension divides over immigration and Europe is the result of compositional shifts in the mix of social groups and value orientations in the electorate, the activation of longstanding divides by economic and social changes such as globalization and the rise of the European Union, or some mix of both.

NEW CLEAVAGES?
Interlocking demographic and economic developments are transforming the composition of European electorates, creating the conditions where new cleavages-demarking large, electorally significant groups with clearly defined and opposed interests and values-may emerge (Enyedi 2008). In this section, we review some of these compositional changes and consider their potential impact on patterns of party competition. The changes include (a) the expansion of higher education and the emergence of graduates as a distinctive electorate; (b) mass immigration and the emergence of electorally significant ethnic minority communities; (c) the reactions of socially conservative white voters with the lowest levels of formal education to demographic decline and political marginalization; (d) the unprecedented growth in the size of older cohorts of the electorate thanks to increases in life expectancy; and (e) the emergence of geographical cleavages reflecting the increased segregation of voters into cosmopolitan cities and conservative hinterlands, as well as the divergence of identities and interests resulting from this segregation. These changes to social structure, and to the prevalent sets of beliefs and values within particular groups, create opportunities for existing or new parties to mobilize support-and thus potentially give rise to new dimensions of political conflict, which can change the cleavage structure of political competition.

Educational Expansion
The expansion of higher education has been one of the major social trends in postwar Western Europe, with all countries investing heavily in increasing the availability of university education. As a result, the share of university graduates in the electorate has been steadily rising in all Western European democracies, with very sharp increases from one generation to the next. In the most recent European Social Survey in 2016, graduates make up an average of 32% of the overall population across 15 Western European states, but they comprise 37% of the under 30s and only 21% of the over 70s. Figure 1 plots the percentage of the population holding a university-level qualification between 1992 and 2018. The overall share has more than doubled in just a quarter of a century. In some countries (e.g., Austria, Greece, Ireland, Spain) the increase has been even more pronounced.
University graduates have distinctive social identities, values and interests, so the dramatic expansion of higher education is driving an ongoing compositional shift in the electorate with the potential to create new cleavages and party alignments (Stubager 2008(Stubager , 2009(Stubager , 2010. And there is growing evidence that the mobilization of distinctive graduate electorates and graduate concerns has already been an important factor driving party system change and the emergence of new parties in a number of Western European democracies. The worldview and moral values expressed by graduates are quite different in some regards from those with lower levels of formal education. Early and influential research by Flanagan (1987) and Kitschelt (1994) described graduates as libertarians, who reject social hierarchies and prioritize individual rights and freedoms, and opposed them to authoritarians, who embrace social hierarchies and prioritize maintaining conformity and order. Graduates have embraced the cultural and ethnic diversity that increasingly characterizes Western societies, expressing more positive views toward minority groups (Strabac & Listhaug 2008, Storm et al. 2017) and toward state efforts to Year protect and support these groups through multicultural or antidiscrimination policies (Hooghe & Vroome 2015), while expressing less attachment to traditional majority national identities (Hjerm & Schnabel 2010). In the international arena, graduates favor openness and collaboration; compared with nongraduates, they are more likely to support free trade (Hainmueller & Hiscox 2006), open borders and liberal migration policies (Hainmueller & Hiscox 2007, Hainmueller & Hopkins 2014, and the European Union (Hobolt 2009, Hakhverdian et al. 2013). This cosmopolitan and internationalist stance could reflect distinctive graduate economic interests (Kriesi et al. 2012). Graduates have the technical skills and cognitive capacities to thrive in an integrated global economy and therefore stand to gain from economic and political integration, which opens up new opportunities for them. In addition, graduates who express stronger education-based identities and group consciousness are particularly prone to distinctive behavior, suggesting that there may be an educational analog to the traditional and much-studied concept of class consciousness (Stubager 2013). However, while group consciousness may encourage distinctive behavior, there is little evidence that graduate political behavior is driven primarily by individual self-interest: Enthusiasm for free trade or immigration is typically no greater among individuals who stand to gain directly from them, suggesting that graduates' preferences for such policies is a matter of social principles rather than individual interests (Langsaether & Stubager 2019).
Graduate voters across Europe show a fairly consistent tendency to prefer political parties that display a distinct liberal stance on the second dimension of cultural values and internationalism. This alignment finds expression in various different ways, depending on the mix of political parties available in the national electoral context. Higher education consistently predicts support for European green parties (Dolezal 2010), which typically pair social liberalism with a distinctive internationalist and environmentalist ideology that graduates find appealing (Rüdig 2012 polls. This may reflect the growing salience of environmental concerns as the financial crisis fades: Greens' perceived ownership of the environmentalist cause helps them prosper among younger graduates, who typically hold the strongest environmentalist values, whenever environmentalist causes become locally or nationally salient (Wagner 2012, Abou-Chadi 2016, Grant & Tilley 2019. While green parties mobilize a particular environmentalist value, in other systems socially liberal, politically reformist, and pro-EU parties have also been able to build a distinctive base of support among graduates. In the Netherlands, university graduates with pro-EU and proimmigration stances are the strongest supporters of both the Green Left party and the socially liberal, pro-EU D66 party (De Vries 2018). Emmanuel Macron's liberal reformist En Marche movement similarly won its strongest support from pro-EU and cosmopolitan French university graduates, and university education was one of the strongest predictors of favoring Macron over Marine Le Pen in the 2017 French presidential election (Evans & Ivaldi 2018). University graduates opposed to Brexit in Britain have fueled the recent recovery of the Liberal Democrats, a socially liberal centrist party that strongly opposes Britain's departure from the European Union. University education is also strongly associated with support for the socially liberal, politically reformist Ciudadanos in Spain-particularly outside of its Catalan homeland, where politics is more structured around a center-periphery cleavage (Teruel & Barrio 2016). Mass higher education is thus generating an electoral base for the mobilization of distinctive socially liberal and pro-EU parties across Western Europe, though in keeping with Lipset & Rokkan's (1967) original model, such mobilization takes different forms depending on existing local cleavages and political alignments.

Mass Migration and Ethnic Diversity
Most Western European countries have experienced substantial rises in ethnic diversity driven by mass migration in the last 50 years. The growing migrant-origin ethnic minority populations of Europe are a diverse and complex mix, including labor migrants recruited from poorer countries outside of Europe during the high-growth, full-employment years of the 1960s and 1970s; economic migrants exercising EU freedom-of-movement treaty rights to move from one member state to another; postcolonial migrants resettling from newly independent former colonies to the former colonizer states; and refugees fleeing conflicts in Africa, the Middle East, and the former Yugoslavia (Geddes & Scholten 2016). Most of these migrant-origin communities have features that make them strong candidates to drive a new political cleavage: They have distinct ethnic identities and cultural traditions; they tend to cluster geographically and economically in struggling places and lower-status, less secure parts of the labor market; and they have unique group political interests, in particular for recognition of their cultural traditions and political representation of their ethnic groups, and for protection from majority hostility and discrimination. Figure 2 plots the number of immigrants per year (per 1,000 capita) for Western European democracies between 1998 and 2017. This reveals a rising trend interrupted by the global financial crisis. The figure shows annual arrivals, so the cumulative effect of ongoing mass migration is a steady increase in the foreign-born share of the population across Western Europe.
Research on the political behavior of ethnic minorities is most extensive in Great Britain, where mass migration began somewhat earlier than in the rest of Western Europe and where migrants were unusually well integrated into electoral politics due to British laws granting full political rights to all migrants from former colonies and territories of the British empire from the moment of arrival (Hansen 2000). British researchers have also gathered unusually rich data on migrant minority communities, including two election studies specifically aimed at ethnic minority voters . This loyalty appears to be rooted in a strong sense of group identity and "linked fate" (Dawson 1994)-ethnic minority voters recognize that they have a collective group interest in eliminating discrimination and other forms of structural disadvantage, and this collective group interest leads them to support the Labour Party as the only party that has repeatedly legislated to address such issues. Migrant-origin minority communities have been less extensively researched in the rest of Europe, where their political emergence has been slower due to widespread barriers to citizenship and political rights. This is now rapidly changing in most Western European countries, as the liberalization of citizenship rules (Koopmans et al. 2012), the increasing naturalization of long-term resident migrants, and the emergence of large native-born second-generation migrant-origin communities (Heath et al. 2008) all contribute to the rapid growth of ethnic minority electorates. The patterns established early in Britain appear to be repeating in other Western European societies: Migrant and ethnic minority communities, often facing considerable hostility and prejudice from parts of the native population (Helbling 2012), have gravitated toward center-left parties (Wüst 2004(Wüst , 2011Teney et al. 2010;Bergh & Bjørklund 2011;Michon & Tillie 2011;Tiberj & Michon 2013;Strijbis 2014), which make greater efforts to respond to minority concerns by fielding ethnic minority candidates (Bloemraad & Schönwälder 2013, Dancygier 2017 and by passing laws that protect minority cultures and sanction discrimination (Bird et al. 2011). There have been exceptions to this general pattern. In Germany, the large Aussiedler migrant community-ethnic Germans who have migrated to Germany from across Eastern Europe-tend to align strongly with the center-right CDU/CSU, reflecting the longstanding support from the center-right for this migrant community (Wüst 2004). In the Netherlands, DENK, a party specifically focused on representing ethnic minority voters and fighting discrimination, split off from the main center-left party in 2015 and has won strong support particularly from Dutch Muslim minority communities, becoming in 2017 the first explicitly ethnic minority-focused party to win seats in a Western European Parliament (Otjes & Krouwel 2019).
There are strong structural, psychological, and organizational factors that should stabilize and reinforce distinctive group-based patterns of political behavior as European polities become steadily more diverse. Ethnic minority communities have strong group identities, grounded in religious and cultural traditions that set them apart from the majority and reinforced by the suspicion and discrimination they still face all too frequently from parts of the native population. They also have strong organizational structures, often built around religious institutions, which enable them to mobilize politically around their group interests (Sobolewska et al. 2015). What is less clear is whether the current alignment with center-left parties will persist as minority populations grow and become more politically integrated. If other European countries follow the British example, then ethnic minority voters will become an increasingly important electorate for centerleft parties, yet it may also become steadily harder to retain their loyalties without antagonizing other important parts of the center-left electoral coalition (Schmidtke 2016). The socially conservative views of many migrant minorities (particularly Muslims) are at odds with the secular and socially liberal sentiments of the growing electorate backing the left on second-dimension social values grounds, while efforts to better represent and respond to minority communities risk inflaming nativist sentiments among older native voters with low education levels. The emergence of large ethnic minority electorates could facilitate the renewal of center-left parties, or it could catalyze their disintegration, with graduates, ethnic minorities, and nativist white voters scattering in different directions.

The Decline of White School Leavers
Radical right parties have now emerged as a substantial organized political force in practically all Western European democracies. White voters who leave formal education with the lowest level of qualifications or no qualifications at all-a group we hereafter call white school leaversare the core electorate of this party family everywhere (Betz 1993, Mudde 2007, Rydgren 2008, Wagner & Meyer 2017, Norris & Inglehart 2019. Traditionally, unskilled and skilled manual workers shared socioeconomic interests and were mobilized via social democratic parties. With the decline of traditional industries, unions, and associated social/community institutions, as well as the shift of many left parties toward the center, this social group has become partially unbound from the labor-capital cleavage-leaving it increasingly up for grabs politically. The radical right has capitalized on the threat white school leavers perceive from the rise of immigration and ethnic diversity, and the alienation produced by their demographic decline and political marginalization, to mobilize them into the basis of a new, identity-and values-driven alignment.
The mobilization of the radical right has destabilized the traditional class cleavage in many countries, driving a wedge between center-left parties, which package progressive economic policies with support for migration and the European Union, and economically left-wing but authoritarian nationalist working-class electorates (Rydgren 2012, Oskarson & Demker 2015, Oesch & Rennwald 2018. This generates a growing dilemma for center-left parties. The long-term decline of working-class electorates encourages them to seek additional support from middle-class progressive and ethnic minority voters, yet the socially liberal and cosmopolitan values of such voters are at odds with the authoritarian nationalism of their traditional working-class electorate (Bale et al. 2010). Center-left parties can seek to resolve this dilemma if they can find new "bundles" of issues that appeal to both their new and traditional electorates (Abou-Chadi & Wagner 2019), but this task is greatly complicated by defensive and hostile reactions to demographic decline among ethnic nationalist white voters. The center-right faces a related dilemma (Bale 2003). Center-right parties cannot ignore the competition they face from the radical right for socially conservative and nationalist voters, but trying to stem such losses by adopting stronger stances on radical right issues or bringing radical right parties into coalition (De Lange 2012) risks reputational damage with more moderate voters while legitimating the radical right (Van der Brug et al. 2005, Harteveldt & Ivarsflaten 2018.
Compositional change is a central part of this story. Mass immigration (Ivarsflaten 2008), rising ethnic diversity (Rydgren 2008), and the emergence of significant Muslim populations (Ford & Goodwin 2010, Helbling 2012) all serve as "situational triggers" (Sniderman et al. 2004) that activate latent authoritarian sentiments in the white school leaver electorate (Stenner 2005, Stenner & Haidt 2018, mobilizing them behind radical right parties who campaign against such threats. Perceptions of demographic decline ( Jardina 2019) and the loss of political influence (Gest 2016) also help drive the emergence of racialized and xenophobic white nationalist identities in this group, particularly when these perceptions interact with economic marginalization (Carreras et al. 2019). Radical right parties mobilize such latent anxieties through a narrative that emphasizes conflict between the declining white school leaver group and the rising groups of graduates and ethnic minorities-framing themselves as the defenders of the "true people" or "real people" whose identity and interests are being marginalized by "cosmopolitan liberals," "globalist elites," and "alien" migrant minorities (Rooduijn & Akkerman 2017, Nai 2018. The emergence of the radical right meets all the classic criteria for a new political cleavage. It involves a stable pattern of alignment by a demographically distinct electorate with a clear sense of identity and shared interests, who have been organized into politics by parties articulating and packaging these interests (Bornschier 2010, Wagner & Meyer 2017. This cleavage follows the Lipset & Rokkan (1967) pattern-while there is a common set of demographic and social trends driving its emergence, national political contexts frame the form of its political expression. The most successful radical right parties have often been established parties that previously mobilized a different agenda before shifting to nationalist, anti-immigration messages. The radical right parties of Denmark, Norway, and Austria began as economically right-wing parties mobilizing traditional economic cleavages, while the Swiss People's Party began life as an agrarian party mobilizing the rural-urban cleavage. An established place in the party system gives such radical right parties "reputational shields"-credible arguments to combat charges of intolerance when they shift to a nationalist, anti-immigration agenda (Ivarsflaten 2006). Radical right parties also vary in the out-groups they mobilize against. While immigrants and Muslim minorities are a focal point in most contexts, in Britain the UK Independence Party and subsequently the Brexit Party have drawn on longstanding nationalist suspicion of the European Union (Ford et al. 2012, Ford & Goodwin 2014; in Belgium the Vlaams Blok and Vlaams Belang have drawn upon a tradition of separatist Flemish sentiment (van Haute et al. 2018); and in Spain the radical right has broken through by mobilizing nationalist opposition to Catalan separatists (Turnbull-Dugarte 2019). Although the particular form of radical right mobilization varies from context to context, the common theme across Western Europe is the unmooring of a large group of low-skilled white working-class voters from the traditional labor-capital conflict and their growing alignment with second-dimension conflicts over national identity, diversity, and immigration. While the breakaway radical right social base is smaller than its predecessor, and projected to continue to shrink over time, it is also highly cohesive in terms of its authoritarian and nationalist positions on these new issues, making the radical right a stable and persistent feature of party cleavage structures across Western Europe.

Aging Societies
Economic development, advances in health care, changing lifestyles, and expansion of welfare states have led to sustained increases in life expectancy across Europe. In 1967, the year that Lipset & Rokkan published their original thesis, the average life expectancy in Western European countries was 70.6 years (World Bank 2019). By 2017, this had reached 80.6 years. Combined with lower birth rates, the shape of the age pyramid of European countries is changing-the share of the population aged 65 or older has risen from roughly one in ten when Lipset & Rokkan wrote to nearly one in five today, with further rises expected. Older voters thus make up a growing bloc of the electorate, who are politically distinctive both because of their greater propensity to turn out to vote (Blais & Rubenson 2013) and because voters gravitate to the political right as they move into old age (Tilley & Evans 2014). Figure 3 reveals the steady aging of Western European societies and significant growth of this part of the electorate. An aging population creates potential for a new cleavage to emerge. Older voters tend to be insulated from economic shocks to labor markets (since most are retired from full-time employment), are more likely to hold assets (specifically, to own their own home), and are not exposed to future costs of issues like climate change. Due to their point in the life cycle, this group is also reliant on the state for retirement benefits, health services, and social care; population aging therefore steadily increases the budgetary pressures faced by governments providing these services. These common interests are layered on top of significant generational differences in value orientations (e.g., Tilley & Heath 2007, Grasso et al. 2019. While age significantly structures the ideological difference of individuals both on the traditional left-right dimension and on the social liberalism-conservatism dimension-such as on the issues of immigration, same-sex marriage, and climate change-there is scant evidence that age differences yet explicitly structure party competition. The most notable exception is 50PLUS, a Dutch party advocating for pensioners' interestsbut it received only around 3% of the national vote in parliamentary elections in 2017. While older voters do have shared interests, these have to date been well catered to by established political parties-who often rely on them due to their greater propensity to turn out to vote. Thus, while the so-called gray vote has the potential to structure ideological conflict, the heterogeneity of beliefs and interests within generations ultimately means age is not yet being mobilized as a new cleavage. Different generations reflect the particular balance of social structure (such as education or social class) at a given point in time. For example, younger people are more likely to have been to university and less likely to have been employed in manual or routine occupations. As such, age often highlights the presence of other cleavages but is itself not the defining line of ideological conflict (though intergenerational economic fairness and climate fairness are increasingly salient issues).

Place as a Cleavage
The rediscovery of geography as a cleavage of electoral politics is a notable feature of contemporary democratic debate in Western Europe and elsewhere. Support for radical right parties and candidates has been clustered in peripheral, often former industrial, areas-what Rodríguez-Pose (2018) calls "the revenge of the places that don't matter." In contrast, advances made by socially liberal and green parties have been concentrated in major cities and thriving towns. As Rodden (2010Rodden ( , 2019 argues, the geographical distribution of ideological preferences in industrial societies is not coincidental but rather reflects historical processes of economic activity and residential choices-with those processes combining sorting, self-selection, and contextual effects. These changes in how voters are distributed across a country can impact party competition by creating or reinforcing geographical cleavages.
In economic terms, a contemporary geographical cleavage is being created by agglomeration and globalization (Rickard 2020)-with particular urban forms, notably mega-city regions and smaller high-tech towns, acting as magnets for population and skills (Sassen 2001, Moretti 2013, while many peripheral towns, cities, and regions are experiencing relative depletion of their human and economic capital (Martinez-Fernandez et al. 2012). In 1950, 65% of the population of Western Europe resided in urban areas; that figure is projected to reach 87% by 2050 (United Nations 2018). Across many advanced industrial economies, these processes are increasingly sorting populations with particular characteristics (which map closely onto the other new cleavages discussed here) into particular places. As mega-cities attract younger, more skilled populations and migrants due to opportunities for education, employment, and cultural consumption, more peripheral towns and rural areas often are increasingly experiencing rapid population aging, combined with outflows of economic activity and people (especially younger generations). These outflows are especially acute in areas that have experienced the decline of traditional industries, such as former manufacturing towns. Nearly one in five of all migrants reside in the world's 20 largest cities (European Political Strategy Centre 2017). Economic agglomeration is thus shaping a geographical cleavage due to polarization in the mixes of people living in different areas: the young, educated, more ethnically diverse populations of major cities are more likely to hold socially liberal values, whereas the older, less educated, and more ethnically homogeneous populations of outlying regions tend to hold more populist and socially conservative outlooks ( Jennings & Stoker 2016. While such demographic sorting has been central in the structuring of this geographical cleavage, the self-selection of particular social groups into particular places is a further contributing factor. Gallego et al. (2016, p. 546) find geographical sorting in the British context driven by self-selection: "an individual's existing political preference is a strong and significant predictor of the political orientation of the area into which he or she moves." In a study of immigration attitudes in large European cities, Maxwell (2019, p. 472) notes the presence of both sorting and self-selection effects: "Large European cities have more positive immigration attitudes than rural areas because those cities have larger percentages of residents who are highly educated and professionals and because people with positive immigration attitudes self-select into large cities." The sorts of people who move to urban centers tend to be more liberal in outlook, even after controlling for demographics. Segregation of populations via sorting and self-selection has powerful effects, Enos (2017) argues, on social cognition-and thereby on intergroup trust and social and political conflict. Geographical segregation is also consequential depending on how electoral systems translate preferences into seats (i.e., via majoritarian or proportional systems). Rodden (2010) argues that the urban concentration of left parties under first-past-the-post systems has historically restricted their representation. The clustering of social liberals and ethnic minorities in cities may have similar effects in systems where geography plays a role in translating votes to seats, weakening the potential influence of highly concentrated electorates.
The final way in which geography matters for sharpening lines of political conflict is through the impact of context on perceptions of in-and out-groups, and on feelings of relative political and economic status. In her study of Wisconsin politics in the United States, Cramer (2016) observes how rural resentment of urban elites is interlinked with perceptions of relative political and social status; rural and small-town residents link the economic decline of these peripheral areas to political favoritism toward metropolitan areas and the liberal voters residing in them. Similar dynamics also are plausible in Europe. The gilets jaunes movement in France has manifested a discontentment with metropolitan Paris elites in a further expression of the urban-rural divide that was already evident in voting for the Front National's Marine Le Pen in the 2017 presidential election. The 2016 Austrian presidential election revealed a similar polarization of the electorate between core cities and the peripheral hinterland, in an election that pitted a cosmopolitan green academic against the radical right. In their analysis of the Brexit vote, Carreras et al. (2019) find that people who live in economically depressed and declining areas are more likely to develop anti-immigrant and Eurosceptic attitudes, while elsewhere the radical right similarly capitalize on relative economic decline (Patana 2018). More generally, McKay (2019) finds that in Britain the populations of less densely populated areas are more politically discontented, even after controlling for relative affluence of those areas. Adler & Ansell (2019) argue that house prices-themselves a function of the relative economic trajectories of particular areas-are associated with perceptions of local decline that can drive populist voting. Through these processes, populations are increasingly sorted and self-select into particular areas, with local context reinforcing the stark geographical distribution of political preferences-structuring the ideological conflict between cosmopolitan-liberal and socially conservative values. The reawakening of center-periphery conflicts in new forms thus looks likely to once again play an important role in structuring European party competition.

CONCLUSION
The social conflicts that were once frozen into the party systems of Western Europe have been transformed by a century of social and economic change. While the remnants of those historic cleavages still shape electoral politics today, party systems have been fractured by the emergence and mobilization of a second dimension of European politics-which is argued to derive variously from postmaterialism, globalization, and European integration. This new dimension is revealed by the now widely recognized advances of radical right, green, and social liberal parties at the expense of social democratic, Christian democratic, and conservative parties. There has to date been relatively limited focus on the impact of more recent and ongoing changes in social structure that are central to this continuing evolution of Western Europe's political cleavages.
We have identified four key socio-demographic developments that are contributing to the emergence of new cleavages in European democracies. First, educational expansion has driven the growth of a mass graduate class and the corresponding decline of school leavers with few educational qualifications, who were often employed in manual and unskilled occupations. A second important development is mass migration and the growing ethnic diversity of European electorates. Third, the aging of societies contributes to deepening generational divides-both in terms of other demographic characteristics (such as education) and political values and identities. Fourth is the growing geographical polarization of populations between prospering major cities and declining towns and rural areas. While the rise of new parties and the fragmentation of party systems reflect the strategic mobilization of electorates in an era of instability and volatility, these long-term changes in European societies are fundamental to understanding political change.
If Lipset & Rokkan (1967) are correct, in the long term new parties will emerge or old parties will redefine themselves in response to these shifts in the composition of the electorate and the new divides they bring to the fore. This may go well beyond the recent advances of new parties as challengers in Western European party systems-in time these new cleavages may come to dominate, rather than simply disrupt. Existing parties may of course adapt and find ways to absorb these cleavages into their platforms, but there should be no mistake that the lines of ideological conflict are a-changin'.
We have set out here some reasons why these demographic changes have the potential to transform the cleavages structuring Western European politics. One feature of the debate over the rise of the radical-authoritarian right has been the defining role of culture-in terms of values and identities-above economic change. In many regards, the literature on both political sociology and party competition has neglected the ways in which all of these developments in social structure are intrinsically entangled with the contemporary capitalist model in advanced industrial countries: knowledge economies requiring highly skilled labor (and corresponding decline of employment in traditional industries), open economies that rely on migrant labor, and a focus on urban agglomeration as a driver of growth. These dynamics-shaped through the dominant policy model of advanced industrial economies-have driven the growth of the graduate class, the decline and marginalization of the working class, high migration and rapidly rising ethnic diversity, and the growing geographical segregation of populations between core and peripheral areas. Aging societies, in contrast, are a product of economic (and scientific) development, and to the extent that there are significant differences in political attitudes by generation, these tend to reflect the particular composition of different generations (such as in rates of education, their relative position in the economic structure, and their tendency to be located in particular places). These are not coincidental features of advanced industrial societies but defining features of their political economy, which are central to shaping electoral competition.
Thus, while globalization and European integration are often the focus of analysis on new dimensions of politics, these are expressions of a more fundamental transformation of the economic model of advanced industrial societies-shifts in the underlying demographic structure of those societies which are giving rise to new cleavages that are either already finding political expression or lying in wait for future waves of political change. It is these changes in social structure that matter most in the final analysis, more than the apparent winners and losers at any particular point. It is cleavages, such as those of education, ethnicity, class, and place, that define and divide society's winners and losers, and shape the political contests between them.

DISCLOSURE STATEMENT
The authors are not aware of any affiliations, memberships, funding, or financial holdings that might be perceived as affecting the objectivity of this review.

LITERATURE CITED
Abou-Chadi T. 2016. Niche party success and mainstream party policy shifts-how green and radical right parties differ in their policy impact.