We compared negative and positive ads in the context of a fictitious election. Participants read a strong or weak message supporting one candidate (positive ad) or derogating the opposition candidate (negative ad). The strong positive message had a greater impact on attitudes toward the candidates than the weak positive message, but message strength had no significant effect for negative messages, suggesting that positive messages are centrally processed, and negative messages serve mainly as peripheral cues. Accordingly, a strong positive message was more effective than a weak positive message, but a weak positive message was less effective than a weak negative message. We conclude that negative political ads are advisable only when candidates cannot provide strong arguments to support their candidacy.