Congress today is falling short. Fewer bills, worse oversight, and more dysfunction. But why? In a new volume of essays, the contributors investigate an underappreciated reason Congress is struggling: it doesn’t have the internal capacity to do what our constitutional system requires of it. Leading scholars chronicle the institutional decline of Congress and the decades-long neglect of its own internal investments in the knowledge and expertise necessary to perform as a first-rate legislature. Today’s legislators and congressional committees have fewer—and less expert and experienced—staff than the executive branch or K Street. This leaves them at the mercy of lobbyists and the administrative bureaucracy. The essays in Congress Overwhelmed assess Congress’s declining capacity and explore ways to upgrade it. Some provide broad historical scope. Others evaluate the current decay and investigate how Congress manages despite the obstacles. Collectively, they undertake the most comprehensive, sophisticated appraisal of congressional capacity to date, and they offer a new analytical frame for thinking about—and improving—our underperforming first branch of government.