Crossing Party Lines: Volatility and Ticket Splitting in Mexico (1994–2000) DAVID CROW Department of Government, University of Texas, Austin, USA This article aims to amplify our portrait of the Mexican electorate by examining the ways in which Mexican electors distributed their votes among the parties during 1994–2000, both over successive elections (volatility) and in the same election (ballot splitting). Aggregate and survey data revealed that Mexicans engaged in these two forms of electoral behaviour frequently, indicators of an electorate in flux. Regres- sion analysis indicated that, contrary to the expectation that the polit- ically sophisticated differentiated their votes, virtually all parts of Mexican society were equally likely to switch parties and split tickets. Keywords: ballot splitting, electoral behavior, Mexico, volatility. In all countries that desire to preserve political liberty, there must be an opposition party. (Andre ´s Quintana Roo 1816) 1 Introduction 2 The tonic note in Mexican politics for the past decade (at least) has been the advance of opposition parties at the expense of the dominant Institutional Revolutionary Party 1 Quintana Roo, Andre ´s, ‘Sobre la necesidad de que existan partidos de oposicio ´n’. In Justo Sierra, Luis G. Urbina, et al., Antologı´a del Centenario, p. 194, Secretarı´a de Educacio ´n Pu ´blica (SEP): Mexico City, 1985 (1st edition, 1910), original emphasis (author’s translation). 2 The author extends his heartfelt thanks to Dr. Peter Ward, director of the Mexican Center of the University of Texas at Austin; Dr. William Glade, former director of the UT Austin Mexican Center, which provided a travel grant for electoral observation in July 2000; and Dr. Rau ´l Madrid for invaluable advice. Many people south of the Rı´o Bravo also contributed with typically Mexican generosity: Mtro. Jaime Rivera Vela ´squez, Director de Organizacio ´n Electoral, Instituto Federal Electoral (IFE); Lic. Jorge Lo ´pez Coutigno, Director de Comunicacio ´n Social del Congreso de Morelos; Lic. Antonio Sa ´nchez Acosta, Instituto Electoral del Estado de Me ´xico (IEEM); Lic. Alejandrina Rojas Estrada and Lic. Salvador Placencia, Instituto Electoral del Distrito Federal (IEDF); and Lic. Elı´as Peralta and Lic. Marcelo Rangel, Instituto Electoral de Morelos (IEM). # 2005 Society for Latin American Studies. Published by Blackwell Publishing, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA. 1 Bulletin of Latin American Research, Vol. 24, No. 1, pp. 1–22, 2005