Friends and Foes: How Coalition Formats Shape Voters’ Perceptions of the Party System

This study looks at the effect of coalitions between parties on how similar citizens perceive the parties that participate in these coalitions to be. We build on different strands of literature to argue that citizens use information on which parties coalesce with each other as a heuristic to make judgments about the similarity of these parties, and that partisan identifiers of the parties in question should be especially sensitive to this signal. We test these claims using panel survey data from the German state of Baden-Wuerttemberg, collected between 2011 and 2016, a phase in which the party system went through profound changes in government composition, especially with the Green-Christian Democrat coalition formed in 2016. We find that while coalitions do indeed make the parties involved appear more similar, how this effect plays out depends largely on the structure of the party system.