Ideal Points in Mexico¿s Congress: ¿Individual Traits or Partisan Ties?; Puntos ideales en el legislativo mexicano: ¿características individuales o pertenencia a partidos?

This study analyzes the ideological positions of members of the Mexican Chamber of Deputies from 2009 to 2015 by estimating ideal points. It explores whether these positions are primarily explained by party affiliation or by individual characteristics such as gender, Single Member District legislators, and previous status as substitute legislators. The wnominate scaling method was applied to non-unanimous roll-call votes from legislatures LXI, LXII, and LXIII to estimate ideal points in a two-dimensional space. Then, linear models were used to examine the distance between each legislator and their party¿s average position. Party affiliation strongly predicts ideological placement. However, female deputies, majority rule elected members, and former substitutes show distinct patterns of proximity or distance to their party lines, varying by conflict dimension and legislature. The emergence of a new anti-system party (Morena) significantly shifts the political spectrum by positioning itself in opposition to the ruling party. The study is based on a limited sample of votes and legislative periods, which restricts generalizability. Nevertheless, it offers valuable insights into legislative behavior in Mexico and points to future research on the role of other personal attributes in shaping political representation. © 2025, Universidad Nacional Autonoma de Mexico. All rights reserved.