This paper explores the development of four electorally consolidated populist parties, i.e. the Italian FSM and Northern League, Podemos in Spain and the French FN. Adopting a supply-side approach based on the ‘thin-ideology’ paradigm, we propose a fine-grained analysis of the populist claims by those parties comparatively. We argue in particular that populism must be considered as both ideology and political strategy, and that populist parties are context-specific forms of political mobilization. Whilst parties such as the FSM, the LN, the FN and Podemos exhibit core people-centered and anti-elite features of populism, there is little research on the conceptualization by those parties of the ‘people’ and the ‘elite’. We examine the ideational processes whereby populist parties construct idiosyncratic notions of the “people” and the “elite”, and the chains of equivalence they employ to reorganize the political forces in their socio-political environment. An important source of variation in the supply of populism across all four cases can be found in the competitive positioning of those parties and their location in the party system. The second part of this paper looks at populism as political strategy and a context-specific form of political mobilization, which includes also the role of charismatic leadership and party organization. To examine these aspects, we adopt a common analytical framework which we apply to each of our four populist cases successively.