Political competitition and multiparty coalition governments

Abstract. Many previous theoretical analyses of multiparty coalition behaviour have been based either on a one-dimensional policy model or on a constant-sum game interpretation. For theoretical and empirical reasons this paper focusses on a competitive two-dimensional model. In this model parties are concerned with policy outcomes but choose party positions both with a view to electoral consequences and as a basis for coalition bargaining. The political heart is proposed as the set of possible coalition outcomes. The heart is either the core of the political game or is determined by a small number of party positions. Under certain conditions an equilibrium in the choice of party positions can be shown to exist. The model suggests that parties can be categorized as either strong or weak core parties, anti-core parties or peripheral parties. This categorization of parties implies a typology of party systems, which gives some theoretical foundation for the occurrence of minority, minimal winning and surplus coalitions in many of the European countries in the postwar period.