June 23, 2021, 12:30–13:30
While digital platforms have facilitated protests and challenged democratic norms, mass online campaigns could also enhance electoral accountability. We evaluate the electoral impact of non-partisan Facebook ads informing millions of Mexican citizens of municipal expenditure irregularities in 2018. Vote shares of the least malfeasant incumbent parties increased by 7-8 percentage points in directly targeted electoral precincts. This effect was greater where ads targeted 80%—rather than 20%—of the broader municipal electorate. These substantial impacts of widely shared social media campaigns reflect interactions between citizens that spill through social networks, including to untargeted precincts, rather than responses by politicians or media outlets.