Are Voter Decision Rules Endogenous to Parties’ Policy Strategies? A Model with Applications to Mass Depolarization in Post-Thatcher Britain

While spatial modelers assume that citizens evaluate parties based on their policy positions, empirical research on American politics suggests that citizens' party support often drives their policy preferences, rather than vice-versa. Building on previous findings that partisanship is less salient to European citizens than to Americans, we argue that when European party elites are polarized on salient policy dimensions then citizens will typically update their partisanship to match their policy preferences, rather than vice-versa. We further argue, however, that because policy salience declines when parties converge, European citizens may cease to update their partisanship in response to parties' policy positions when the parties are not sufficiently polarized on a focal policy dimension – even if, in absolute terms, the parties remain meaningfully divided on the dimension. We evaluate these hypotheses via individual-level analyses of British election panel survey data between 1987-2001, a time period during which party elites converged on social welfare policy, and find support for our arguments. We show that our findings illuminate the aggregate-level depolarization patterns that occurred in Britain during the post-Thatcher era, and have important implications for parties' policy strategies and for political representation