This study goes beyond the analysis of the causes of the emergence of populist actors in the party system, focusing instead on those cases in which populism and its counterpart anti-populism, translate into an ideological and discursive divide that contributes to structuring a certain party system. When populism/antipopulism emerges as a political cleavage, the factors behind parties’ political choices in general and electoral coalition preferences in particular, can be affected. For this new cleavage, to start to polarize, a change in the political opportunity structure is needed. In fact, when the political opportunity structure opens as a consequence of events external to the party system new actors may enter the system, producing a change in the dynamic of competition. Moreover, considering the organizational density of the parties in the system, defined as the power of penetration of a given party, in terms of both intensity and reach, this dissertation can shed light on the likely duration not only of the parties but also of the cleavage.
