Mainstream political parties across Europe increasingly face electoral competition from challenger parties. In particular, the consistent success of radical right parties (RRPs) is closely linked to their core issue of immigration. How should mainstream centre-right and centre-left parties respond to the new issues politicised by RRPs, if they wish to maintain their dominant positions within party systems?

In a classic study, Meguid (2005) proposed that mainstream parties have three possible strategies: dismissive, adversarial, or accommodative. However, each strategy carries electoral risks, and existing research offers mixed results on their relative effectiveness. This paper revisits the debate by considering the heterogeneity of voter motivations and the specific political contexts in which mainstream parties attempt to accommodate radical right positions. The analysis draws on an original observational study of a unique case of accommodation in Germany ahead of the 2025 legislative elections, alongside a cross-national experimental study conducted across Europe.