Public Persuasion with Endogenous Fact-Checking

Abstract

We study public persuasion when a sender communicates with a large audience that can fact-check at heterogeneous costs. The sender commits to a public information policy before the state is realized, but any verifiable claim she makes after observing the state must be truthful (an ex-post implementability constraint). Receivers observe the public message and then decide whether to verify; this selective verification feeds back into the sender's objective and turns the design problem into a constrained version of Bayesian persuasion. Our main result is a reverse comparative static: when fact-checking becomes cheaper in the population, the sender optimally supplies a strictly less informative public signal. Intuitively, cheaper verification makes bold claims invite scrutiny, so the sender coarsens information to dampen the incentive to verify. We also endogenize two ex-post instruments - continuous falsification and fixed-cost repression - and characterize threshold substitutions from persuasion to manipulation and, ultimately, to repression as monitoring improves. The framework provides testable predictions for how transparency, manipulation, and repression co-move with changes in verification technology.