When Can Political Parties Credibly Change Their Policies?

When can a party credibly change its policy on an issue? No institution forces parties to keep their promises after being elected. Voters may thus view platform shifts as mere pandering, discounting their credibility. We propose that voters use the direction of a platform shift as a signal of the party’s motives and policy commitment. Shifting to an unpopular position is a costly signal of principled motives, while moving toward a popular one suggests opportunistic ones. Two preregistered survey experiments, one evaluating a general setting and another focusing on a real case of mainstream party accommodation to the radical right, show that voters infer party motives and commitment from platform shifts in line with the predictions of our argument. Our study provides important insights into the electoral persistence of radical right parties, party system stability, and why platform shifts often fail to affect voter perceptions of party positions.