This analysis clarifies and extends several underdeveloped but significant new components of Jurgen Habermas's public sphere theory. At center stage is the distinction between public communication's critical and warning functions. Communication scholars have long recognized the public sphere's critical function of filtering public opinion. But few have acknowledged its warning function of alerting political decision-makers about widespread but privately experienced social problems. This warning function deserves more attention for two reasons. First, it clarifies how the political public sphere interacts with civil society and the state through means other than rational-critical debate. Second, it represents a phase of public communication in which strategic action serves as a necessary antecedent to formalized decision-making. Implications for critical theories of the public sphere and communicative action are discussed.