To rule or not to rule? An experimental study of the electoral ramifications of claims to (not) rule with radical right populist parties

In a between-subjects experiment ( n = 3270) conducted in Flanders (the Dutch-speaking part of Belgium), we examine the electoral ramifications of claims by a right-wing mainstream party on their willingness to rule or not with RWPPs (radical right populist parties). Participants were exposed to a social media post by the largest right-wing party (New Flemish Alliance, N-VA) in which it either accepts or rejects ruling with the main RWPP in Flanders (Vlaams Belang, VB). Findings reveal a main effect on propensity to vote (PTV) for the RWPP: in the inclusion condition the propensity to vote for the RWPP is significantly higher than in the exclusion condition; this holds particularly for policy-driven voters. The mainstream party, however, nor gains or loses electoral support. This suggests a legitimization effect: claims by mainstream parties on willingness to rule with RWPPs serves the former, while mainstream parties do not gain electorally.