This article presents the results of an experiment that looks at the relationship between electoral systems, strategic voting and the effective number of electoral parties. The study is based on experiments conducted with groups of 21 participants. The experiments consisted of a series of elections involving four parties. Two main treatments were applied. First, four different voter distributions were created. Second, there were two kinds of electoral systems under which the subjects voted. The analysis indicates that voters do not coordinate on the same parties under different electoral rules. Importantly, we find that the classic type of strategic voting identified by Duverger (1954) is reinforced by a different type of strategic voting identified by Cox (1997), namely "strategic amplifying voting". The results show that classic strategic voting reduces the effective number of electoral parties while strategic amplifying voting increases the latter. Overall, we show that voters' strategic behaviors mediate the impact of the electoral system on the effective number of electoral parties.
