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.