Guillermo Trejo is Associate Professor of Political Science at the University of Notre Dame and Faculty Fellow at the Kellogg Institute for International Studies. He was previously on the faculty at Duke University and at the Centro de Investigacin y Docencia Econmicas (CIDE) in Mexico City.

Trejo's research focuses on collective action and social protest, armed insurgencies and political violence, and religion and ethnic identities in authoritarian regimes and new democracies. He is the author of "Popular Movements in Autocracies: Religion, Repression and Indigenous Collective Action in Mexico" (Cambridge University Press, 2012). His work has been featured in the American Political Science Review, the Journal of Latin American Studies and Poltica y gobierno. Trejos doctoral dissertation received the 2006 Mancur Olson Award from the Political Economy Section of the American Political Science Association and his research on religious competition and ethnic mobilization in Latin America received the 2011 Jack Walker Outstanding Article Award from the APSA Political Organizations and Parties Section.

Trejo is currently working on a new research agenda on organized crime and violence in new democracies. Whereas his previous work sought to explain the rise and transformation of peaceful social movements into armed insurgencies and their impact on democratization, his current research seeks to explain the rise of organized crime, its transformation into criminal insurgencies, and its impact on the quality of democracy. He is working on a book provisionally entitled Votes, Drugs, and Violence: Democratization and Organized Crime in Latin America.

This book presents a new explanation of the rise, development and demise of social movements and cycles of protest in autocracies; the conditions under which protest becomes rebellion; and the impact of protest and rebellion on democratization. Focusing on poor indigenous villages in Mexico's authoritarian regime, the book shows that the spread of U.S. Protestant missionaries and the competition for indigenous souls motivated the Catholic Church to become a major promoter of indigenous movements for land redistribution and indigenous rights. The book explains why the outbreak of local rebellions, the transformation of indigenous claims for land into demands for ethnic autonomy and self-determination and the threat of a generalized social uprising motivated national elites to democratize. Drawing on an original dataset of indigenous collective action and on extensive fieldwork, the empirical analysis of the book combines quantitative evidence with case studies and life histories.