Las dimensiones de la competencia en el sistema de partidos mexicano (1979-2012).

This article focuses on the major transformations in the Mexican party system that occurred during the protracted process of democratic transition; it is divided into three parts. The first part is a brief review of the factors that contributed to the process of political-electoral change. In the second part, we carry out an analysis of changes in a number of dimensions of the Mexican party system, based on aggregate electoral data at national and district levels, as well as on data from public opinion surveys. The third part presents an analysis of the ideological structure of political competitiveness based on data from surveys on the left-right ideological stances of Mexican federal legislators. The paper shows important changes in the structure and behaviour of the Mexican electorate, such as increasing partisan de-alignment, as well as a growing level of competitiveness and fractionalization of the party system. [ABSTRACT FROM AUTHOR]