Pre-electoral coalitions (PECs) are one of the most often used methods to coordinate entry into the electoral market. Party elites, however, do not know how voters will respond to the coalition formation at the polls. In this article, the authors report on an experimental study among 1,255 Belgian students. In order to study voter responses to the formation of PECs, respondents were presented with two ballots: one with individual parties (party vote condition) and one with coalitions (coalition vote condition). The aim of this experiment is to predict under what conditions party supporters will follow their initially preferred party into the coalition and vote for the PEC, and under what conditions they would desert the PEC at the polls. The decision whether to follow the coalition or not can be traced back to four considerations: dislike of the coalition partner; ideological congruence between coalition partners; size of the initially preferred party; and being attracted to a specific high-profile candidate. (Dis)liking the coalition partner is independent from the ideological congruence between the two coalition partners. The study’s results also show support for an adjustment effect, as respondents became more loyal toward cartels over the course of the 2003–2005 observation period.
