This paper develops a signaling theory of competitive political action. Despite the free rider problem associated with mass political participation, rational and self-interested individuals may take costly political action to inform or manipulate a policymaker’s decision. The individuals on one side of the issue generally have stronger incentives to become active than do those on the other side. The policymaker rationally takes into account differential participation incentives when extracting information from the political action turnout on each side. As a consequence, asymmetric participation incentives do not cause a systematic policy bias in favor of the more active side. This result contrasts with the commonly held view that political decisions will tend to be biased in favor of interests that are more successful in overcoming the free rider problem of political participation.