The electoral success of radical right parties throughout Western Europe is the biggest change to these formerly stable party systems. Several studies have identified that mainstream parties can shape the trajectory of radical right parties. Our aim is to contribute to this literature, and to investigate if and how radical right parties gain from mainstream party recognition. Theoretically, we draw on the literature that has suggested that when aiming to explain the legitimization of radical right parties, we need to consider that many individuals in Western Europe are influenced by an anti-prejudice norm when forming preferences towards such parties. We hypothesize that when mainstream parties signal that it is acceptable to associate with radical right parties’ they challenge the anti-prejudice norm that dissuade voters from such parties. In addition, individuals with lower internal motivation to control prejudice (IMCP) are more susceptible to be affected by mainstream party recognition of radical right parties as those with high IMCP have a stronger internalized anti-prejudice norm. We evaluate the effects of changes in the normative context in a survey experiment (N = 1133) by manipulating mainstream party legitimization of a radical right party, the Sweden Democrats, before the Swedish parliamentary election in 2018. Our results suggest that when mainstream parties challenge the anti-prejudice norm, individuals are more likely to sympathize with radical right parties. Moreover, the effect of mainstream party recognition is moderated by IMCP – individuals with a low motivation to appear non-prejudiced are more influenced by mainstream party legitimization of a radical right party.