When people feel ambivalent toward an information source, their attitudes toward the endorsed information reflect the influence of contextual priming. In particular, the valence of relevant (i.e., applicable to source evaluations) and irrelevant (i.e., not applicable to source evaluates) media contexts likely exert influences through conceptual and affective priming, respectively, such that they polarize message persuasion in diverging ways. Using celebrity endorsers in ads, Experiments 1 and 3 show that valence of a relevant story about similar people triggers conceptual priming and generates context contrast effects on endorsed information among ambivalent, but not univalent, participants. In contrast, Experiments 2 and 3 show that valence of an irrelevant article triggers affective priming and generates context assimilation effects on endorsed information among ambivalent, but not univalent, participants.