Decomposing political advertising effects on vote choices

This paper studies the channels through which political television advertising influences individuals' voting decisions. Scholars are interested to learn whether advertising primarily persuades people to change their choices of candidates or mobilizes people to vote. I find that advertising does both: about 60% to 70% of advertising's effect is persuasion, and 30% to 40% of it is mobilization. Advertising's effects are stronger on those who did not plan to vote for a major-party candidate. To decompose the impact into its components, the present paper estimates a multinomial probit model that permits analysis of decisions of turnout and candidate choice jointly in a Markov chain framework. In contrast to most studies that estimate the effects of aggregated exposure to advertising on voters' choices on Election Day, I study how advertising influences peoples' monthly voting intentions leading up to Election Day. In the context of the 2008 presidential election, the magnitude of the advertising effect is not large enough to overcome John McCain's significant deficit, but it potentially could have changed the outcomes of other close elections such as those in 2000 and 2016.