Do Online Ads Influence Vote Choice?

Abstract

Do online ads influence vote choice? We partner with a German party to evaluate the effectiveness of online ads using a cluster-randomized experiment. During the 2016 Berlin state election, 189 postal districts were randomly assigned to (a) emotional ads; (b) factual ads; or (c) no ads. Analyzing electoral results at the postal district level, we find that the overall campaign weakly increased the party’s vote share by 0.7 percentage points (p-value = 0.155). We also estimate a negative effect of the campaign on the vote share of the party’s main competitors of 1.4 percentage points (p-value = 0.094). Turning to the mechanism of persuasion, we find that the factual ads, if anything, fared slightly better than the emotional ads. Our evidence thus provides tentative support that online ads positively affect vote choice.