UsingPetrocik's (1996)theory of issue ownership as a point of departure, I develop and test a theory of “trait ownership” that provides an explanation for the origins of candidate trait perceptions and illustrates an important way that candidates affect voters. Specifically, I argue for a direct connection between the issues owned by a political party and evaluations of the personal attributes of its candidates. As a result, the American public views Republicans as stronger leaders and more moral, while Democrats hold advantages on compassion and empathy. I also draw on “expectations gap” arguments from psychology and political science to demonstrate how a candidate may gain an electoral advantage by successfully “trespassing” on his opponent's trait territory. National Election Studies data from the 1980–2004 presidential elections are used to demonstrate the existence, durability, and effects of trait ownership in contemporary American political campaigns.