Electoral system for national legislature

Mexican Constitution as amended in 2015 (Constitución Política de los Estados Unidos Mexicanos), accessed29 August 2024

ARTICLE 52. The House of Representatives shall be integrated by 300 members, who shall be elected according to the principle of majority voting through the uninominal voting system in all the electoral districts; and the remaining 200 members shall be chosen according to the principle of proportional representation, using a system of regional lists voted in multimember districts.

ARTICLE 53. The borders separating the 300 uninominal electoral districts from each other shall be set down after dividing the country’s population by the number of districts, taking into account the most recent census. Each state shall have at least two representatives elected under the principle of majority voting.

In order to elect 200 representatives under the principle of proportional representation, using a system of regional lists, five multimember electoral districts shall be established in the country. The law shall set down the ways in which such territorial division will be made.

ARTICLE 54. The election of the 200 representatives under the principle of proportional representation, using a system of regional lists, shall be subjected to the following principles:

I. To register its regional list, a political party must prove that it participates with candidates to the House of Representatives to be elected by the principle of majority voting in at least two hundred uninominal districts.

II. Every political party attaining at least three percent of the total votes casted for the regional lists at the multimember constituency shall be entitled to have representatives under the principle of proportional representation.

III. The political party complying with the two principles above established, shall obtain the number of representatives from the list corresponding to each multimember district, according to the way the people vote on that constituency. The order established in the regional lists shall be respected to appoint the candidates.

IV. No political party shall have more than 300 representatives, regardless the principle by which they have been elected.

V. The political parties shall never have a number of representatives by both principles, which considered in percentage of the House, exceeds by eight points the percentage they have obtained in vote. This restriction shall not be applied to the political party that, due to its electoral victories at uninominal districts, obtains a percentage of seats greater than the addition of the percentage obtained in national vote plus eight percent.

VI. After that seats have been distributed according to previous paragraphs III, IV and V, the leftover proportional representation seats shall be awarded to the remaining political parties which have a right in each one of the multimember districts, in direct proportion to the national and effective votes received by these parties. The law shall regulate procedures and formalities to apply this article’s principles.

300 FPTP; 200 List PR using closed list and largest remainder