Persuasion and Information Aggregation in Elections

This paper studies a large majority election with voters who have heterogeneous, private preferences and exogenous private information about an unknown state of the world. We show that a Bayesian persuader can achieve any state-contingent outcome in some equilibrium by providing additional information. In this setting, without the persuader’s additional information, a version of the Condorcet jury theorem holds, in the sense that outcomes of large elections satisfy full-information equivalence (Feddersen and Pesendorfer, 1997). Persuasion does not require detailed knowledge of the voters’ private information, preferences, or the voting rule. It also requires almost no commitment power on the part of the persuader.