Why do constituents sometimes defer to their representative's judgment, rewarding her for acting as she thinks best, even when she ignores their demands? By making decisions about trust, constituents determine whether their representative is rewarded for implementing their demands or for using her judgment. These decisions shape legislator behavior and, through behavior, policy outcomes. Therefore, any attempt to explain or evaluate representative institutions such as the modern Congress requires an answer to a simple question: When do constituents trust their representative, and what is the basis of that trust? This book is the first systematic analysis of constituent trust. It assumes that elected officials and ordinary citizens are rational actors. However, the book moves beyond the standard rational choice framework in three ways. It avoids narrow, unrealistic assumptions about motivations and information. It shows that many kinds of behavior not usually thought of as rational choices, such as a voter's desire to be represented by "someone like them," are the product of a systematic, predictable calculus---a calculus aimed at securing favorable policy outcomes. Finally, the book uses interviews with ninety-three members of the U.S. House of Representatives to test its predictions about trust.