The theory of strategic voting has been tested in experiments for elections in single member districts with three candidates or parties. It is unclear whether it can explain strategic voting behavior in a fairly common type of political system, multi-party systems with proportional representation, minimum vote thresholds, and coalition governments. In this paper, we develop a (non-formal) strategic voting game and show in a simulation that the model produces election scenarios and outcomes with desirable characteristics. We then test the decision-theoretic model in a laboratory experiment. Participants with a purely instrumental (financial) motivation voted in a series of 25 independent elections. The availability of polls and coalition signals by parties was manipulated. The results show that voters are frequently able to make optimal or strategic vote decisions, but that voters also rely on simple decision heuristics and are highly susceptible to coalition signals by parties
