Party system dynamics and the making and breaking of Italian governments

This paper explores the dynamics of the highly fluid Italian legislative party system. It uses the same theoretical approach as the paper by Laver and Kato (this issue) to explore the making and breaking of governments in Italy following electoral reform. Under office-seeking motivational assumptions, the electoral system provides incentives for parties to band together into cartels in order to fight elections, with the winning cartel forming a government coalition. Inter-electoral legislative party competition, however, within a structure of permissive rules on the formation of legislative party groups, provides incentives for at least some members of the winning cartel to defect. The facility with which legislative parties can split and combine in Italy creates a highly dynamic decisive structure underpinning the making and breaking of governments. This cannot usefully be analysed with traditional models that take parties as unitary actors and assume that the party system is essentially fixed for the entire inter-electoral period.