Abstract: We provide a comprehensive assessment of the influence of television advertising on United States election outcomes from 2000–2018. We expand on previous research by including presidential, Senate, House, gubernatorial, Attorney General, and state Treasurer elections and using both difference-in-differences and border-discontinuity research designs to help identify the causal effect of advertising. We find that televised broadcast campaign advertising matters up and down the ballot, but it has much larger effects in down-ballot elections than in presidential elections. Using survey and voter registration data from multiple election cycles, we also show that the primary mechanism for ad effects is persuasion, not the mobilization of partisans. Our results have implications for the study of campaigns and elections as well as voter decision making and information processing.