A Two-Party System Under the Proportional Rule is Possible: Strategic Voting in the Lab

In this study, we implement a series of voting games in the laboratory to test whether a strategic voting behavior in a proportional system would arise and induce a two-party system. In each voting game, a finite number of subjects with single-peaked preferences, uniformly distributed on a 0–20 line, are asked to vote for a number within the interval 0–20. The policy outcome is the average of the chosen numbers—a realistic representation of a compromise between parties in a parliament elected through the proportional rule. Our main result shows that polarization and strategic voting occur in the proposed proportional rule scenario. Moreover, experience and information concerning the electoral outcome of the previous period drive individuals to opt for strategic voting.