Filibusters and efforts to defeat them shape the public reputation of U.S. senators and their parties. I develop a formal model to study how senators' concerns about their own and the opposing party's reputation influence their behavior in the Senate. In the model, a majority and opposition party bargain over policy. Each party earns a reputation with a core primary constituency which observes legislative bargaining and forms beliefs about its party's policy priorities. Filibusters and attempts to defeat them are costly and can therefore credibly signal that a party values a particular issue. I identify conditions under which parties use these costly procedural moves to preserve or enhance their reputation when the costs of obstruction deter purely policy-motivated parties from filibustering or attempting to defeat a filibuster. Alternatively, under certain conditions parties strategically choose not to pursue policy victories that they otherwise would either to protect their own reputation with a constituency that values other issues more highly or to deny the opposing party the opportunity to signal. I examine the model's empirical implications for the relative frequency of filibusters, cloture votes, and tabling motions and identify conditions under which the Senate is endogenously supermajoritarian.