Despite the explosion of populism research, there is a shortage of comprehensive analyses of the ideational varieties of populist parties and of the different roles they play in contemporary party systems. In order to overcome such limitations, I provide a state-of-the-art review of the literature on the classification of populist parties and make three innovative contributions to populism research. First, by adopting a truly pan-European perspective to cover, in addition to EU member countries, contexts that are generally overlooked, including but not limited to Liechtenstein, Russia, Serbia and Ukraine, this review article provides an empirical application of the ideational approach to populism to 66 contemporary parties. Second, it highlights the major shortcomings of common approaches to the study of populist parties in contemporary party systems, which almost invariably treat them as ‘challengers’ or ‘outsiders’. Finally, it pushes the agenda further by providing a classification and empirical overview of the three interactive patterns characterizing the 66 populist parties under analysis: non-integration, negative integration and positive integration.

On the occasion of the fiftieth anniversary of the concept of anti-system party it is time to ask whether it enjoys good health in addition to longevity. Reflecting on what constitutes an anti-system party appears to be of unprecedented relevance, particularly in the light of the electoral success of populist parties such as the French Front National, the Five Star Movement in Italy and Syriza in Greece. This article highlights two crucial questions that remain unsolved if we follow existing conceptualizations: What are the boundaries of the concept? When does a party cease to be anti-system and how can it be reclassified thereafter? In order to overcome such limitations, this article develops a revisited concept of anti-system party and provides a set of guidelines for its empirical application. Furthermore, a novel typology capable of investigating the evolution of anti-system parties and classifying political parties in general is presented.