The dissertation examines the use of background appeals in campaign messages. I argue that background appeals allow campaigns to meet two seemingly conflicting incentives in the same message—the incentive to reduce voters’ uncertainty about their candidate, and the incentive to remain ambiguous in their issue positions. Background appeals allow voters to know more about a candidate and develop more certainty about what he will do in office. At the same times, campaigns can achieve this goal while avoiding specific policy commitments, which, on controversial issues, might repel a significant part of the electorate. I test my argument by examining how campaigns plan on using candidates’ backgrounds by interviewing a sample of political consultants. The consultants I interviewed make the candidate’s background a top priority in developing a message plan for their clients. They want to show voters “who their candidate is” as a means of developing likeability and credibility with voters. As expected, campaigns use background appeals frequently, in nearly 80% of advertisements aired by US Senate campaigns in 2000 and 2002. But in these appeals, campaigns avoid specifically connecting their candidate to particular policies. Also, the appeal of ambiguity is so great that campaigns only use more specific background appeals when discussing the opponent’s background. Background appeals can have a positive effect on perceptions of a candidate. Using an experimental design, I vary the background of a mock candidate for Congress while holding constant his issue position. Respondents regard the candidate more favorably when they learn about his occupation than when they receive no such information. / text