Opinion Polls, Coalition Signals and Strategic Voting. : Evidence from a survey experiment

Recent studies find that defection from one's most preferred party to some other party is as common under proportional representation (PR) as it is in plurality systems. It is less elaborated how election-specific contextual factors affect strategic vote choice under PR. This study looks at the impact of two potentially important contextual factors: parties’ coalition signals about cooperation with other parties (referred to as ‘pre-electoral coalitions’) and polling information, which vary from one election to the next. The focus is strategic voting for smaller parties at risk of falling below an electoral threshold. The hypothesis is that parties that are included in well-defined coalitions will benefit from strategic ‘insurance’ votes if the polls show that they have support slightly below the threshold. However, smaller parties that do not belong to a coalition would be less likely to benefit from insurance votes. Extensive survey experiments with randomized coalition signals and polls give support to the idea that a voter's tendency to cast an insurance vote depends on whether the polls show support below or above the threshold and whether the party is included in a coalition or not