David J. Samuels is the Benjamin E. Lippincott Associate Professor of Political Science at the University of Minnesota. He is the author of Ambition, Federalism, and Legislative Politics in Brazil (Cambridge University Press, 2003) and the co-editor of Decentralization and Democracy in Latin America (2004). He has published articles in the American Political Science Review, the Journal of Politics, Comparative Politics, Comparative Political Studies, Legislative Studies Quarterly, and the British Journal of Political Science.

Matthew S. Shugart is Professor at the Department of Political Science and the School of International Relations and Pacific Studies, University of California, San Diego. Among his books are Seats and Votes (with Rein Taagepera, 1989), Presidents and Assemblies (with John Carey, Cambridge University Press, 1992), Presidentialism and Democracy in Latin America (co-edited with Scott Mainwaring, Cambridge University Press, 1997), Executive Decree Authority (co-edited with John Carey, Cambridge University Press, 1998), and Mixed-Member Electoral Systems (co-edited with Martin Wattenberg, 2001). His articles have appeared in numerous journals, including the American Journal of Political Science, the American Political Science Review, the British Journal of Political Science, and Electoral Studies.

This book provides a framework for analyzing the impact of the separation of powers on party politics. Conventional political science wisdom assumes that democracy is impossible without political parties, because parties fulfil all the key functions of democratic governance. They nominate candidates, coordinate campaigns, aggregate interests, formulate and implement policy, and manage government power. When scholars first asserted the essential connection between parties and democracy, most of the world's democracies were parliamentary. Yet by the dawn of the twenty-first century, most democracies had directly elected presidents. David J. Samuels and Matthew S. Shugart provide a theoretical framework for analyzing variation in the relationships among presidents, parties, and prime ministers across the world's democracies, revealing the important ways that the separation of powers alters party organization and behavior - thereby changing the nature of democratic representation and accountability.