The Role of Labor Unions as Political Machines: Evidence from the Case of the Mexican Teachers’ Union * Horacio A. Larreguy † Cesar E. Montiel Olea ‡ Pablo Querubin § March 2014 Abstract In this paper we analyze the electoral role of the Mexican teacher’s union as a po- litical machine. To study its effect on electoral outcomes, we exploit variation across time in its political alliances, whether polling stations are located in schools –which fa- cilitates the machine’s operation– and its strength across Mexican states. Our findings suggest that the candidates supported by the machine of the teacher’s union experience a significant increase in their vote share when a polling station is located in a school. However, such an effect is only present in the areas where the leadership of the teacher’s union exerts influence over its affiliates. We also show evidence that is consistent with the fact that SNTE uses electoral results at a low level of aggregation to monitor school directors and teachers. JEL: D72, J51 Key words: electoral fraud, labor union, political machine. * This paper benefited from helpful conversations and suggestions from Andrei Gomberg, Emilio Guitierrez, and Marco Morales. Participants at the MIT Political Economy Workshop and 2013 NEUDC Conference provided essential feedback. We are greatly indebted with Elisa Lavore and Lucrecia Santiba˜ nez who helped us with the data on the dissident local school sections. Alejandra Menchaca and Sahar Parsa provided support and patience throughout the project. All errors are our own. † Department of Government, Harvard University, Cambridge, MA (hlarreguy@fas.harvard.edu) ‡ Department of Politics, New York University, New York, NY (cmo331@nyu.edu) § Department of Politics, New York University, New York, NY (pablo.querubin@nyu.edu) 1