An institutional explanation of party system congruence: Evidence from six federations

Abstract.  The allocation of resources between the federal and state levels of government is a key institutional variable explaining the congruence or similarity of party systems. It affects the incentives voters and parties face, and opportunities for cleavage mobilization. This article pioneers measures for comparing congruence across federations. Evidence from state and federal elections in six federations produces clear evidence that party systems are least congruent in decentralized federations and most congruent in centralized federations. Voter behaviour, indicated by the variation of electoral support for parties across units of the federation and the similarity of swings in support between the state and federal levels, is most responsive to the allocation of resources. Party system structure is less responsive to this variable.