Missing links in party-system polarization: How institutions and voters matter

This article aims to understand the determinants of party-system polarization by moving beyond the (almost exclusive) emphasis placed in the literature on the role of the electoral system and the number of parties. We propose a larger menu of explanatory variables that includes both institutional and voters-related factors. Regarding the institutional factors, we highlight the consequences of expectations of coalition formations as well as office-related elections (e.g., Presidential ones) on party-system convergence in legislative elections. For the voters-related factors, we address the importance of specific characteristics of the electorate following insights from the spatial theory of voting. To test our hypotheses, we use survey data covering 33 nations and 67 elections. While hypotheses derived from electoral systems and number of parties find little empirical support, the new variables that we consider involving institutions and voters matter significantly.