The affect misattribution procedure (AMP) is one of the most promising implicit measures to date, showing high reliability and large effect sizes. The current research tested three potential sources of priming effects in the AMP: affective feelings, semantic concepts, and prepotent motor responses. Ruling out prepotent motor responses as a driving force, priming effects on evaluative and semantic target responses occurred regardless of whether the key assignment in the task was fixed or random. Moreover, priming effects emerged for affect-eliciting primes in the absence of semantic knowledge about the primes. Finally, priming effects were independent of the order in which primes and targets were presented, suggesting that AMP effects are driven by misattribution rather than biased perceptions of the targets. Taken together, these results support accounts that attribute priming effects in the AMP to a general misattribution mechanism that can operate on either affective feelings or semantic concepts.