Abstract
This paper develops a theory of political fact-checking aimed at understanding fact-checkers’ motivations from their observed behavior. We first document two empirical stylized facts: fact-checkers scrutinize one side of the political spectrum more (Re-publicans) and uncover a higher share of false facts from that side. We then develop a model in which two politicians report facts — true or false — to persuade voters. The fact-checker selects one politician and reveals whether their fact is true. We examine several fact-checker motivations, characterizing the probabilities of each politician being fact-checked and the share of false facts detected. Our results show that the empirical patterns are inconsistent with an impartial fact-checker. Instead, these patterns may be explained by a strong bias in favor of Democrats or a weak bias in favor of Republicans. We also characterize the fact-checking strategy maximizing voters’ welfare and discuss the welfare implications of each type of fact-checker.