Ideological, Affective, and EU Polarisation: Mobilising Voters in European Parliament Elections

Political polarisation has moved to the forefront of the study of comparative political science, reflecting societal developments and concerns over its presence and consequences. Recent empirical work has connected citizens’ political polarisation to a range of negative outcomes, such as reduced social trust, social fragmentation, and the rise of anti-democratic behaviour. At the same time, a growing body of research suggests that polarisation can also have positive democratic effects, such as mobilising citizens to participate in elections. For example, ideological polarisation between parties offers citizens a clearer choice at the ballot box, which in turn makes them more likely to vote. Furthermore, affective polarisation – emotional hostility toward other groups of voters – is also likely to stimulate turnout because it raises the personal stake of elections to voters. While this relationship is well-documented at the national level, its relevance to supranational elections remains unclear. Supranational elections, such as those for the European Parliament (EP), are often characterised as second-order elections, where lower stakes and weaker identification with EU institutions result in lower turnout. The unique institutional and political context of the EU – marked by multi-level governance and issues often perceived as distant from voters’ immediate concerns – may therefore condition how polarisation influences electoral behaviour. This makes it critical to investigate whether the polarisation-turnout mechanism also applies to the supranational level of EP elections. In this study, I therefore examine whether polarisation enhances voter turnout in EP elections. Using the 2024 European Election Study, a comprehensive post-election survey conducted across all 27 EU member states, I explore the impact of three dimensions of polarisation on turnout: ideological polarisation, affective polarisation, and EU-specific polarisation over the issue of European integration. For ideological polarisation, I analyse the role of perceived ideological polarisation, measured by voters’ perceptions of divergence in party positions on the left-right dimension. With regards to affective polarisation, I look at the effect of the distribution of sympathy scores toward different voter groups. Finally, I measure polarisation over European integration by looking at voters’ perceived difference of party positions on whether the EU should speed up or slow down its integration process. Preliminary findings suggest that while perceived ideological and affective polarisation increase turnout, their effects vary across member states. Polarisation over European integration, in particular, appears to play a distinct role in EP elections: voters who perceive higher party polarisation over the issue of European integration are more likely to vote than voters who believe that parties have relatively similar views on European integration. These findings underscore the importance of understanding how polarisation operates in the context of EP elections, and challenges the notion that they are purely second-order contests. Accordingly, by highlighting the potential of polarisation to mobilise voters even in a supranational setting, this study contributes to a broader understanding of electoral dynamics in multilevel systems.