When Does Party Cooperation Inform Voters Judgments of Policy Proximity? A Cross-National Analysis of Heuristic Use in Multi-Party Democracies

In complex multiparty democracies, citizens face the challenge of interpreting elite behavior to locate parties on the policy spectrum. This paper investigates when and why voters use party cooperation as a heuristic for judging the distance between their own preferences and those of an out-party. Drawing on the theory of ecological rationality, I argue that cooperation becomes an efficient heuristic when it is cheap to access, simple to apply, and accurate enough to guide inferences about policy alignment. Using original surveys from Canada, Denmark, Germany, and the United Kingdom across fifteen policy domains, I show that perceived cooperation is consistently associated with reduced policy distance. The effect is strongest among knowledgeable partisans, on polarized issues, and when the out-party is perceived to be ideologically extreme. These findings reveal how ecological rationality conditions voter reasoning, highlighting cooperation as a dynamic elite cue that shapes mass perceptions and democratic representation.