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This paper proposes a reflection on approaches to the study of political party systems and how they have changed. It begins by making a distinction between the two main research methods: the classical comparative approach, which is based on typologies and therefore on analyses based on categories, and an approach using quantitative variables, which is used in transnational surveys in particular. Both of these approaches make it difficult to understand change in party systems, which they reflect too rarely or too frequently. The paper goes on to propose a new approach to the analysis of party systems by returning to the very definition of the concept, i.e. the structuring of competition to control executive power. Finally, a discussion is proposed on the two main changes in party systems: the disappearance of anti-system parties, and the transformation of party-based organizations.