Four studies investigated whether political allegiance and salience of outgroup membership contribute to the phenomenon of acceptance of false, stigmatizing information (smears) about political candidates. Studies 1-3 were conducted in the month prior to the 2008 U.S. Presidential election and together demonstrated that pre-standing opposition to John McCain or Barack Obama, as well as the situational salience of differentiating social categories (i.e., for Obama, race; for McCain, age), contributed to the implicit activation and explicit endorsement of smearing labels (i.e., Obama is Muslim; McCain is senile). The influence of salient differentiating categories on smear acceptance was particularly pronounced among politically undecided individuals. Study 4 clarified that social category differences heighten smear acceptance, even if the salient category is semantically unrelated to the smearing label, showing that, approximately 1 year after the election, the salience of race amplified belief that Obama is a socialist among undecided people and McCain supporters. Taken together, these findings suggest that, at both implicit and explicit cognitive levels, social category differences and political allegiance contribute to acceptance of smears against political candidates. (Contains 4 figures.)