Mapping the Populism-Euroscepticism Nexus: A Symmetric Index Approach Using CHES 2024

In what ways and to what extent are populism and Euroscepticism linked across European party systems? And which party-level characteristics explain this link? This article introduces a symmetric index that measures both phenomena in parallel by combining position and salience. This addresses the common asymmetry whereby Euroscepticism is operationalized via position alone, whereas populism incorporates both position and salience. Using expert assessments for 279 parties in 31 European countries from the Chapel Hill Expert Survey 2024, we first map the populism–Euroscepticism nexus. We uncover a robust positive association (r = .64), alongside a bimodal party distribution: most parties cluster as either Pro-EU Non-Populist or Eurosceptic Populist, while mixed types are comparatively rare. In a second step, we test underlying party-level factors that may explain the strong connection between populism and Euroscepticism. OLS models confirm a horseshoe pattern - ideological extreme parties score higher than centrist parties - with the GAL–TAN dimension outperforming the left–right dimension in determining the variation of the index. Furthermore, parties with lower parliamentary seat shares score higher. Comparing across party families, the results show that Radical Right parties exhibit the highest mean values, followed by Radical Left parties, while mainstream families (e.g., Liberal, Christian Democratic, Social Democratic) score lowest. The results are stable across alternative index specifications and component level analyses. Substantively, the dominance of GAL-TAN suggests cultural roots: parties emphasizing traditional, authoritarian, and nationalist orientations are systematically more likely to pair populist rhetoric with EU opposition. This helps to explain why Eurosceptic narratives are so prevalent, even in countries where pro EU majorities persist.