Several recent events in Europe have brought back the significance of social class. Most recently, the pandemic uncovered divides between lower-class families without financial reserves, and more wealthy families. Working class people were more exposed to health hazards, and more strongly affected by unemployment, adding to existing inequalities. Beginning a decade earlier, the financial and economic crisis had already exacerbated economic inequalities, and political events such as the Brexit vote showed how regional inequalities can lead to political polarization and controversial political decisions. In addition, extreme political actors have been on the rise, and their success is often explained by economic and social anxieties. How the views and grievances of the so-called "left behind" influence political developments like the vote of Donald Trump, is however less clear. In other words, our understanding of how increasingly unequal social structures lead to specific political outcomes remains limited. This project argues that group identities, and more specifically social class identity, might provide the "missing link" between societal and economic changes and (extreme) political outcomes. It seeks to answer the following questions: How salient are social class identities in Western Europe and what determines their salience? Does inequality lead to more conflict between social classes? What is the role of political actors in shaping social class identities? How important are social class identities for political decision-making? To address these questions, project will develop a theoretical and empirical framework to study social class identity in complex social and economic contexts, by combining insights from political sociology, public opinion research and social psychology. We build on existing research on class voting and on voting for right-wing populist parties by introducing an important component: the strength of group attachment. This is based on the assumption that objective social class might not be politically relevant, unless there is some form of emotional attachment to a specific class. The four suggested work packages will combined provide a broad picture on the role of social class identity in European politics, its sources , its specific content, as well as its consequences for political behavior. Thereby, we contribute to a broader literature about the political consequences of economic inequality. Second, the project will shed light on the role of group identities beyond what is generally considered "identity politics". Further, the project will contribute to our understanding of European parties' strategies and success in mobilizing voters with group appeals, and eventually to our knowledge of the reasons why extreme and populist parties have been successful in Western Europe.