Not everyone suffers equally: The effect of electoral overlap on mainstream party responses to right-wing challengers

The rise of new challenger parties and the introduction of new issues to European party systems has required a strategic response from mainstream parties (MSPs). However, not all MSPs are equally affected by the rise of challenger parties. While this idea has been supported in case studies, there has been a lack of wider comparative studies on the different levels of electoral threat experienced by mainstream parties. In this paper, I introduce a new methodological tool to this literature by drawing on the literature on voter availability. Using Propensity to Vote (PTV) data, I measure the specific threat that anti-immigration challengers pose to MSPs in eight Western European countries, and estimate the impact this has on the positions of MSPs on immigration. I find that a higher threat of losing voters to an anti-immigration challenger is associated with a move towards more restrictive immigration policies; on the other hand, a party’s chance to win voters back from a challenger party has no significant impact on their policy positions. These findings are separate from the electoral success of challengers, implying that MSPs react to the rise of challengers in a nuanced way and are highly aware of the voter groups they compete over.