Digital Advertising in U.S. Federal Elections, 2004-2020

Digital advertising is now a commonplace feature of political communication in the United States. Previous research has documented key innovations associated with digital and its consequences for campaigns elections. However, comprehensive picture spending on remains elusive because challenges accessing analyzing data. We address this challenge unique dataset (N=3,639,166) derived from over 13 million expenditure records reported to Federal Election Commission (FEC) between 2004 2020. Employing machine learning model classify expenditures into nine categories including ads services, paper makes four observations. First, 2020 was watershed election growth campaign spending. Second, there are clear partisan differences resources allocated advertising. Third, platform companies play central role an otherwise market services. Fourth, platforms consultants occupy distinct ideological niche within each party.