This paper models competitive political pressures as a signaling phenomenon. People participate in collective action in support of or against the status quo, or they abstain. Their actions and abstentions inform the decision of a policymaker who may overturn the status quo in favor of a policy alternative. By providing an informational microfoundation for the widely used reduced-form “pressure production functions” and “political influence functions,” the analysis allows me to reexamine the role of the free rider problem in creating a bias towards vocal special interests.

The signaling hypothesis finds empirical support with a study of pro- and anti-Gulf War demonstrations that took place in San Francisco and Kansas City (Missouri) in early 1991.