Causes and Effects of Coalition Preferences in a Mixed-Member Proportional System

This paper adapts features of a model of Brams/Fishburn (1992) on coalition voting to the context of a mixed-member proportional system. We differentiate between a candidate vote which determines the winner of a constituency contest, a party vote which determines the seat shares of the parties in parliament, and a coalition preference for all parties the voter considers acceptable for building a majority government. In contrast to the purely axiomatic contribution of Brams/Fishburn we formulate a descriptive model of choice behavior for a real world political environment. We focus a) on congruence between party/candidate preference and coalition preference b) on congruence between coalition preference and party/candidate vote; c) on congruence between coalition preferences and ticket combinations; d) on sincerity/insincerity of party and candidate vote; e) on causes of ticket splitting. Hypotheses are complemented by information on the voters' expectations. Data base of this paper is a representative national sample conducted during the German parliamentary elections 1998