Gaining new insights by going local: determinants of coalition formation in mixed democratic polities

We develop a simple spatial model suggesting that Members of Parliament (MPs) strive for the inclusion of the head of state’s party in coalitions formed in mixed democratic polities, and that parliamentary parties try to assemble coalitions that minimize the ideological distance to the head of state. We identify the German local level of government as functionally equivalent to a parliamentary setting, such that the directly elected mayor has competencies similar to a president in a mixed national polity. Our findings show that the party affiliation of the head of state is a key factor considered by party members in the legislature when forming coalitions: coalitions in the legislature are more likely to form if they include the party of the head of the executive branch. Furthermore, the policy preferences of the head of the executive branch matter for the legislators’ behavior in the coalition formation process: the smaller the ideological distance between the position of a coalition and the position of the head of state, the more likely a coalition is to be formed