This analysis challenges the consensus that, in post-war Italy the Catholic party [Democrazia Cristiana (Dc)], actively supported by the Catholic Church, fostered a process of vote nationalization. The paper, drawing upon a more fine-grained level of analysis, different statistical measures, and within and across regional models, provides a more nuanced interpretation. According to our analysis, although the Dc effectively acted as a homogenizing agent until the late 1970s, after that decade the processes of modernization and secularization fostered the decline of religious-based politics, and of the Dc itself. Such decline opened the way for the re-emergence of a territorial cleavage and a consequent dis-homogenization of Italian electoral politics. The paper demonstrated that the impact of modernization and secularization on the vote for the Catholic party is more significant considering the five Italy’s geo-political areas rather than the country as a whole. Moreover, the divergent path in the five areas testifies the re-emergence of territory in the Italian electoral behaviour. Territorial heterogeneity, modernization, and secularization were central to the collapse of the Dc.