Populism and ideological convergence: Evidence from a multiparty system

Populist parties have gained significant power in European politics in the last decades, raising concerns about the potentially contagious effect of populism. I study how populist party representation in local councils affects other parties’ ideological positions. I use variation created by close elections to identify ideological shifts resulting from a change in party representation, holding voter preferences constant. I use candidate-level data from a voting advice application to estimate ideological positions, modeling candidates’ responses using item response theory to obtain measures of ideology that are comparable across election years. The results show that increased populist representation causes the ideological spectrum among other parties’ candidates in the municipality to become more concentrated. One additional seat for the populist party reduces the interquartile range of candidate positions by 9 %. While there is initial ideological convergence between mainstream and populist parties, it does not persist as the populist party continues to gain more seats. These effects take place only on the liberal-conservative dimension, while positions on the economic dimension are unaffected. The results demonstrate that increased populist representation influences other parties and causes ideological convergence within the candidate base. •I provide causal evidence of how established parties respond to populist parties.•Supply of populism causes ideological convergence among other parties’ political candidates.•Ideological convergence takes place only on the liberal-conservative dimension.•There is initial ideological convergence between mainstream and populist parties.•Convergence between parties does not persist as the populist party gains more seats.