Keywords: Party factions; Intra-Party politics; Italian party system; Quantitative text analysis; Factionalism.
Literature on party factions has investigated the elements that affect factionalism, and particularly the elements that affect the number of factions. Scholars raised a set of hypotheses that have never been systematically tested. Building on those hypotheses the present work analyzes the determinants of the number of factions within Italian parties from 1946 to 2010. Thanks to a new dataset that allows the estimation of policy positions of factions through a quantitative text analysis of motions presented during party congresses, this paper investigates the effects of intra-party polarization as well as the impact of internal rules and the characteristics of party system. The results show that proportional intra-party rules, availability of resources and internal polarization increase the degree of factionalism. Moreover open-list electoral systems contribute to increase the number of factions but only among parliamentary parties.