Since 2007, partisan competition in Quebec has taken the form of a multiparty system, with four parties now represented in the National Assembly. Within this new context, our attention is focused on the Parti Québécois (PQ), which celebrated its fiftieth anniversary in the 2018 election year, but at the same time experienced a major electoral setback, marking another stage of the ongoing erosion of its electoral support in the Quebec population. In this study, we examine the generational dynamics of electoral behaviour in Quebec in an attempt to identify some of the reasons for the decline of the PQ. Data from five post-election surveys (2007-2018) show that the sources of the PQ’s decline are to be found among the youngest cohorts and are linked to their attitudes toward diversity and state interventionism, and especially their support for sovereignty.