Margaret E. Keck is Professor of Political Science at the Johns Hopkins University. She is the author of The Workers' Party and Democratization in Brazil and the coauthor of Greening Brazil: Environmental Activism in State and Society. Kathryn Sikkink is McKnight Presidential Chair in Political Science and Regents Professor of Political Science at the University of Minnesota, and is an affiliated faculty member at the University of Minnesota Law School. Her other books include, as author, Ideas and Institutions: Developmentalism in Brazil and Argentina and, as coeditor, Restructuring World Politics: Transnational Social Movements, Networks, and Norms.