Do citizens punish or incentivize mainstream party legitimization of far right challenger parties?

When competing with new challenger parties, mainstream parties must choose whether they portray the challenger undemocratic or democratic. Often, we could observe mainstream parties shifting from the former (i.e., a delegitimizing strategy) to the latter (i.e., a legitimizing strategy). However, either of these may either backfire or bring rewards to mainstream parties depending on how citizens evaluate these strategies. I examine the case of Sweden, where the mainstream right has shifted from initially delegitimizing the far right to currently legitimizing it. Overall, the findings of a survey experiment (N=2,029) suggest that legitimization of the far right is a consequential choice for mainstream parties. Legitimizing the far right is perceived as more fair, more democratic, and more principled than a legitimizing strategy by the mainstream right’s core constituencies. Hence, mainstream parties face a dilemma. On the one hand, the public does not punish, but even incentivizes mainstream parties to legitimize. On the other hand, pursuing a legitimizing strategy also locks mainstream parties in as they cannot turn back to a delegitimizing strategy.