The legislative consequences of Mexico's mixed-member electoral system, 2000-2009

The emergence of mixed-member electoral systems across the globe has been an attempt to balance local representation through single-member districts (SMD) with programmatic representation through proportional representation lists (PR). However, there are several competing theoretical interpretations for the consequences of mixed systems on legislative bodies. Through a study of the Mexican Chamber of Deputies, I test several empirical implications of these competing theories by examining the impact of the electoral system on party discipline, participation, and legislative organization. I find little convincing evidence of differences between legislators elected through PR and those elected through SMD in their levels of party discipline, but I do find that PR legislators participate in a manner theoretically consistent with their mode of election. I also find that PR legislators have disproportionate control over key leadership positions. I suggest the primary reasons for these findings is due to differing methods of candidate selection and restricted use of dual candidacy.