This study examines citizens' perceptions of fairness and legitimacy in political advertising. Using focus groups, an original national survey, and data on election 2000, as well as drawing on results from a replication of the national survey in 2004, we characterize political ads from the citizen's perspective. We then turn to the impact of ''negative'' advertising on voter turnout. Like several studies, we find circumstances under which turnout can be increased by negative ad criticisms. However, we show that this general result is only part of the story. Drawing on research in political psychology, we suggest that voters are ''motivated processors'' of advertising claims; as such, they evaluate the fairness of an ad according to their partisan predispositions. We show that when partisans perceive the criticisms of their own party's candidate to be fair, they are less likely to say they will vote. As a result, we find that negative advertising not only may affect the total turnout in an election but also has an important and varying impact on the composition of the electorate.H ow does ''negative'' campaign advertising affect the American electorate? In recent years the impact of negative ads has been the subject of a great debate fueled by diverse methodologies and equally diverse answers. Political scientists and pundits have been especially alarmed by suggestions that negative ads may affect partisans and independents differently, depressing turnout for the latter, while stimulating turnout of the former. Concerns about the influence of political advertising, including misgivings about the increase and impact of negative campaign ads, are a subset of two more general issues confronting the American polity: worries about declining participation in elections and the prospect of an increasingly polarized electorate. Given perceptions of the high stakes and close contests of the 2000 and 2004 presidential elections, the precise composition of the electorate at the polls is also of critical interest. Our research offers new evidence about how voters characterize ''negative'' or ''attack'' ads and, in light of these characterizations, how negative ads affect electoral participation, polarization, and composition. We demonstrate that voters' partisanship substantially colors perceptions of legitimate negativity in advertising and that these characterizations in turn affect who goes to the polls. As a consequence, some negative advertising campaigns may stimulate while others depress overall turnout, but more than the total turnout is at stake. Negative advertising also affects the composition of the electorate since partisans and independents experience an advertising stimulus (or deterrent) differently.Electoral campaigns are increasingly ''going negative'' as Geer (2006), among others, has documented. In the decade since Ansolabehere and Iyengar (1995) published findings showing that negative advertising depressed voter turnout, especially among Independents, other scholars have criticized their methodology (Bar...