Party Cohesion, Party Factions and Legislative Party Discipline in Italy

Moving beyond a unitary actor assumption that models members of a self-evidently collective entity such as a political party “as if” they all shared a single brain, this paper explores the cohesion and discipline of party legislators in multi-party systems operating under the constitutional rules of parliamentary government. We do this in the context of Italian politics, for which a consistent received wisdom is that many of the main political parties have a well-defined factional structure, with intra-party factional politics driving how parties behave in the wider political system. We first review some of the theoretical issues arising from treating political parties as endogenous coalitions of politicians, exploring the incentive structure of legislators at the levels of electoral, legislative and executive politics. We then elaborate these issues at an empirical level by mapping the internal factional structure of the main Italian left-wing party, DS (Sinistra Democratica /Democratic Left), then using this to explain why different DS deputies regularly voted in different ways on the same key foreign policy roll calls. We gratefully thank Elisabetta De Giorgi, an invaluable source of information about the Italian DS. Prepared for delivery at the 2005 Joint Workshop Sessions of the European Consortium for Political Research: Granada, 13-19 April. PARTY COHESION, PARTY FACTIONS AND LEGISLATIVE PARTY DISCIPLINE IN ITALY/ 2