Populism has become a widespread phenomenon across Western Europe, especially after the economic crisis of 2008. However, we can still observe some confusion in the academy and the media about the definition of populism, which has led to a very contested and vague use of the term. This article aims to contribute to the conceptual clarification of populism, analysing its presence in a selection of political parties in four Western European countries, and separating the core elements from those of their host ideologies. In order to reach our goals, we conducted a content analysis of a selection of electoral manifestos of eight political parties: Podemos, Sinn Féin, United Kingdom Independence Party and Swiss People’s Party (populist parties); Spanish Socialist Workers’ Party, Labour Party, Conservative Party and Green Liberal Party of Switzerland (non-populist parties from the same countries). Regarding the methodological approach, we ran a classical content analysis and Key Words in Context content analysis. On the one hand, our results confirm that the minimal definition of populism used in this research is consistent to differentiate between populist and non-populist parties. On the other hand, conclusions also show that host ideologies are the main source of divergences between populist parties, especially the presence or absence of nativism.