Does party polarization at the national level influences turnout in EU elections? A multidimensional party competition approach to polarization and electoral participation in second-order elections

An increasing number of studies make the case that EU elections are turning into first-order contests, particularly due to the rising electoral participation observed since the 2019 EU elections (Gattermann et al., 2022). Nonetheless, the explanations for this increase in turnout in EU elections remain unclear. While there is an extensive literature on the impact of polarization on turnout in national contests (Moral, 2017; Ellger, 2023; Le Corre-Juratic, 2024), as well as on the rise of politicization of the European integration at the party system level (Braun et al., 2016; Braun, 2021; Beaudonnet and Gomez, 2024), EU studies have not yet systematically analysed the relationship between party polarization at the national level and electoral participation in EU elections. This is surprising given that EU studies inform us that citizens rely on national cues in the EU context, either to evaluate the European political regime (Harteveld et al., 2013) or to make voting decisions, such as punishing or rewarding incumbents based on their national record (Marsh and Hix, 2011). Most importantly perhaps, it remains unclear how different dimensions of the European issue (economic vs. cultural EU integration) relate to participation in EU elections, even though recent studies on polarization highlight the necessity to take into consideration multidimensionality when assessing the relationship between polarization and voter turnout (Le Corre-Juratic, 2024). Departing from these lines of literature, we explore the idea that polarization will raise the stakes of second-order contests, potentially mobilizing groups that typically do not participate in EU elections depending on the dimensions that are emphasized in party competition. This study seeks to explore these questions by examining the effects of the different dimensions of polarization on electoral participation in EU elections in a longitudinal and comparative perspective. To do so, we employ a two-stage research design using both aggregate and individual level stages and leverage data from the European Election Studies and the Chapel Hill expert survey, covering more than two decades (1999 to 2024). By doing so, this study bridges the gap between the literatures on polarization and second-order electoral dynamics and provides new insights into the role of multidimensional polarization in shaping electoral participation in non-national contests.