The best estimate of the effects of campaign contact & advertising on Americans' candidates choices in general elections is zero

Kalla, Joshua and Broockman, David E., The Minimal Persuasive Effects of Campaign Contact in General Elections: Evidence from 49 Field Experiments (September 25, 2017). Forthcoming, American Political Science Review; Stanford University Graduate School of Business Research Paper No. 17-65. American Political Science Review, forthcoming, available at SSRN: https://ssrn.com/abstract=3042867

Abstract: Significant theories of democratic accountability hinge on how political campaigns affect Americans' candidate choices. We argue that the best estimate of the effects of campaign contact and advertising on Americans' candidates choices in general elections is zero. First, a systematic meta-analysis of 40 field experiments estimates an average effect of zero in general elections. Second, we present nine original field experiments that increase the statistical evidence in the literature about the persuasive effects of personal contact 10-fold. These experiments' average effect is also zero. In both existing and our original experiments, persuasive effects only appear to emerge in two rare circumstances. First, when candidates take unusually unpopular positions and campaigns invest unusually heavily in identifying persuadable voters. Second, when campaigns contact voters long before election day and measure effects immediately - although this early persuasion decays. These findings contribute to ongoing debates about how political elites influence citizens' judgments.