Political cultures have usually been studied as static and perhaps monolithic. If any attention has been dedicated to how political cultures change it has been devoted to exogenous factors. In recent years, however, some authors have advocated exploring the role of endogenous factors. In this article, we reflect on the advantages of a comprehensive approach to explaining how political cultures change, embracing endogenous and exogenous factors. We look at peace mobilizations in Italy as a case study, which allows examination of the interactions of the two political cultures of Marxism and Catholicism. Our work suggests some provisional theories about the dynamics that lead to hybridization between different political families. These dynamics can be understood through the genealogy of a 'grammar of responsibility'. We argue that the factors that condition change in political culture relate to both the national and the international political context. We also show how these processes of change occur as a result of collective action, although individuals also perform important functions of co-ordination, brokerage, leadership, and subversion of codes. Moreover, we show that change in political cultures does not occur in a linear manner but follows a shifting course, which alternates periods of innovation and of involution or regression.