Abstract
This paper investigates the influence populist parties exert on other political parties and the party system. Undertaking a national qualitative case studies analysis, we tested four hypotheses: representation gap hypothesis (populist parties pursue a strategy that is designed to exploit gaps of representation by means of emphasizing new or re-vitalizing old conflicts); contagion hypothesis (the rise of populist parties is accompanied with an overall diffusion of populist ideas in the policy agenda of non-populist parties); polarization hypothesis (the rise of populist parties makes party systems more acutely polarised) and elective affinity coalition hypothesis (populist parties enter governing coalitions with other populist parties and also with non-populist parties if the latter also employ at least one of the typical themes of populist discourse, e.g., nationalist, nativist, anti-establishment, Eurosceptic themes).
Results support the representation gap hypothesis: with the populists' electoral success, they represent new issues in parliament. Concerning the contagion hypothesis, case studies offered mixed results: in some countries contagion can be observed, while not in others.
As for the polarization hypothesis, polarization was identified as a clear tendency.