Motivation or ability? Explaining the effect of party polarisation on proximity voting

Previous work finds that party polarisation increases proximity voting. However, there is surprisingly little evidence about how. This article compares the importance of two possible mediators. First, party polarisation reduces the indifference voters have towards parties' policy platforms. As a result, party polarisation should increase voters' motivation to evaluate parties based on policy agreement. Second, party polarisation makes it easier for voters to know the relative positions of the parties, improving their ability to choose the closest party. Drawing on cross-national data from the most recent European parliamentary elections, the voter's motivation is operationalised as the ‘policy differential’ – the spread of party distances relative to the closest party. Similarly, the voter's ability is measured in terms of ‘party position knowledge’, the fraction of parties the voter places in the same order as country experts. A causal mediation analysis shows that both the voter's indifference and their party position knowledge have comparably sized, substantial mediation effects, accounting for the vast majority of the total effect of ideological party polarisation on left-right proximity voting. Therefore, this article contributes rare evidence about the mechanism by which party polarisation leads to proximity voting.