Rapid and controversial, the spread of school choice initiatives across the United States has radically changed political debate about public education. In this book, Michael Mintrom explores the complex world of open-enrollment policies, charter schools and voucher plans to reveal how and why school choice has become a major issue, and he draws important conclusions about how innovative individuals can spur significant change in the policy arena. Policy entrepreneurs - individuals who take up a cause and make it part of the political agenda - have largely remained background figures without clear definition in the policymaking literature. This book is the first comprehensive and systematic treatment of the concept of policy entrepreneurship, providing an important foundation for explaining how policy proposals are initiated, considered, and adopted. Mintrom uses the emergence of school choice in state politics to examine how policy change originates. He shows how policy entrepreneurs have been instrumental in placing school choice onto state legislative agendas, despite the lack of compelling evidence about its merits, and how they use social networks, reframe policy issues, and attempt to shift the sites of policy debate. Blending innovative theory with both qualitative and quantitative investigation, Mintrom explains how energetic individuals made school choice a real choice. In doing so, he changes our broader understanding of how policy is formed.