We use a novel survey experiment with a broadly representative sample to reveal an important phenomenon in voter integration of campaign communications: preference-mediated partisan motivation. When evaluating the credibility of candidate position changes on minimum wage policy (a readily quantifiable and salient issue domain), partisans do not take a new stance at face value, apply universal skepticism, or simply afford more credibility to co-partisans. Instead, they process a candidate’s stance through an interaction between the voter’s partisan allegiance and their own policy preference. Partisans update more when a co-partisan moves closer to them than when the candidate shifts away from them. The opposite pattern emerges with the other party’s candidates: partisans tend to be more receptive if the candidate moves away from them. This feature of campaign message acceptance has profound implications for political communication and our understanding of partisan cognition.