The Informational Content of Campaign Advertising

Understanding the mechanisms by which political advertising affects voters is crucial for evaluating the welfare effects of campaign finance and election regulation. This paper develops a method to distinguish between two alternative mechanisms for advertising influence: an “informative” channel in which voters learn about candidate attributes through advertising, and a “persuasive” channel in which voters can be directly influenced by advertising even if it makes no contribution to the quality of information they possess about the sponsoring candidate. I separately identify the impact of each mechanism on voter choice by taking advantage of variation in voters’ prior information. I first construct a dataset of all television advertisements aired in the 2002 and 2004 US Senate and Gubernatorial elections, matched with voting data at the media-market level. I then construct and estimate a structural model of vote choice that allows for both informative and persuasive effects of advertising. The results are largely consistent with the persuasive hypothesis. Using the estimated parameters, I conduct counterfactual analyses of several alternative campaign finance regimes and discuss implications for voter welfare.