The spectre of populism has been haunting Western European democracies for years, yet genuinely comparative analyses of the phenomenon are still few and far between – something that is all the more surprising given that populism is not necessarily the prerogative of so-called populists but can be adopted by mainstream actors as well. Using data collected through automated content analysis of party manifestos, we capture the level of populism of more than 300 political parties in 11 Western European countries over more than 70 elections. In the context of party system change, we use these original data to address two crucial issues. First, we explore precisely when a party becomes populist. What characteristics of parties and party systems influence how populist a particular party is at a specific election? Second, we look at how electorally rewarding it is for a party to be populist. More specifically, we ask whether populism has a cumulative impact on a party’s electoral fortunes. When do populist parties gain votes and how much do they gain when they do?
