The wisdom of term limits and professional politics has been debated since the time of Aristotle, spurring 'reforms' of legislatures in Athens, Rome, Venice, and in the US under the Articles of Confederation. This book examines recent trends in American states in order to investigate the age-old question of how the rules that govern a legislature affect the behavior of its members and the policies that it produces. The clear and consistent finding is that the two reforms have countervailing effects: whatever professionalization has brought more of, term limits have reduced. This lesson comes from quantitative analyses of data from all fifty states and detailed examinations of legislative records from six states, informed by interviews with over one hundred legislators, staff assistants, lobbyists, journalists, and executive officials.