Abstract

The rise of political polarization has sparked research on heterogeneity in voter responses to election campaign messages. The same political information campaign can persuade some voters while dissuading others. Beyond direct effects, campaigns have indirect effects as exposed voters share messages with peers. The net impact of a campaign depends on whether voters who react positively or negatively are more vocal within their social networks. Leveraging unique features of Argentina’s electoral system, we conducted a randomized experiment during the 2023 presidential election, varying both direct and indirect exposure to a campaign. Partnering with a local NGO, we sent fact-checking leaflets on Javier Milei’s policy proposals to different subsets of voters before both the first round and the runoff. The leaflet campaign reduced Milei’s support among recipients (direct effect) but increased it among their unexposed neighbors (indirect effect), with the latter effect dominating. The interventions in the first round and the runoff had consistent results, and the effects of the first intervention persisted through the runoff. The opposite-sign direct and indirect effects suggest that voters disagreeing with the leaflet message were more likely to discuss it with their neighbors. The results highlight a novel social-network mechanism through which information campaigns can backfire.