The Mexican Electoral System

1. Political Organization

Mexico is a Federal State composed by thirty-two states: thirty-one states and the Federal District (Mexico City), the later being the seat of the Federal Branches. The government system is presidential. Both the power of the Federation and that of the thirty-two states are based on the principle of division of powers among the Executive, Legislative, and Judicial Branches.

The Federal Executive power rests upon the President of the United Mexican States, in each one of the thirty-one states upon the Governor for each entity and in the Chief of Government for the Federal District. All of them are elected every six years and may not be re-elected.

The Federal Legislative Branch is vested upon the Union Congress, which is divided into an Upper and a Lower Chamber. The Legislative Branch of the thirty-two states is single-chambered; those belonging to the thirty-one states are called local congresses and the one for the Federal District is called Legislative Assembly. All legislators are elected for a three-year period, except the members of the Upper Chamber who serve a six-year period.

The Judicial Branch of the federation is vested upon the Supreme Court of Justice of the Nation, made up of eleven ministers elected by the vote of two thirds of the Upper Chamber members, put forward by the President, to serve fifteen-year terms. The Judicial Branch of the thirty-two states is vested upon their respective Supreme Court of Justice.

The Constitution establishes that all the states of the federation must adopt the municipality as the basis for the territorial, political, and administrative division. A municipal Town Hall, elected through public and direct voting, administers each of the 2,441 municipalities into which the country is divided. Each municipal Town Hall is made up of a Municipal President and a varying number of officers and trustees.

2. Composition and Renewal of the Federal Branches

The Constitution acknowledges the elections as the only legitimate valid method to make up and renew the Federal Executive and Legislative Branches of the states and of the City Councils.

1. Executive Branch

The Supreme Federal Executive Branch rests upon one single member. It is vested upon the President of the United Mexican States. Besides leading the government of the Republic, the President is also Chief of State and the Army. He is elected every six years through direct election, universal suffrage, and the principle of relative or simple majority. The Political Constitution strictly forbids re-election in any modality.

2. Legislative Branch

The Federal Legislative Branch is vested upon the Union Congress, which is divided into an Upper and a Lower Chamber. 500 members who serve for a three-year period and may not be re-elected for an immediate period compose the Lower Chamber, and 128 members who are elected for a six-year period and may only be re-elected after a midterm period, compose the Upper Chamber.

Composition of the Lower Chamber

The Lower Chamber is made up of 500 representatives, all of whom are renewed every three years according to a variation of the personalized proportional representation system in which some of its members are elected by a majority formula and the remaining by a proportional representation formula, under terms that assure a high degree of proportionality between votes and seats.

Therefore, out of the 500 members that make up the Lower Chamber, 300 are elected by relative majority in single-member districts, and the other 200 are elected by proportional representation through the system of party lists in five multi-member districts of 40 seats each.

On this basis, the Constitution establishes two especially relevant provisions regarding the composition of the Lower Chamber:

No political party may have more than 300 Lower Chamber members elected by both principles, that is, relative majority and proportional representation. Thus, if a political party may aspire to the absolute majority of seats (251) due to its electoral performance, the law prevents it from reaching the qualified majority (two thirds of the total seats) required to approve constitutional reforms by the party itself.

In general terms and in order to guarantee proportionality between votes-seats, no political party is allowed to have a total number of Lower Chamber members, that exceeds eight points from the percentage of national votes cast on its behalf. For instance, if a political party wins 35 percent of the election, it will not be entitled to obtain more than 43 percent of the seats, that is, more than 215 of the 500 seats.

The Constitution also establishes that the only exception to this rule shall be in the event that a political party gains a percentage of the overall Chamber seats that exceeds the sum of the percentage of the national votes cast plus 8 percent through relative majority voting in single-member districts. For instance, if a party wins 235 of the single-member districts (amounting to 47 percent of the total), with 35 percent of the total votes cast, the proportionality rule of 8 percent would not be applicable even though the differential between votes and seats would amount to 12 percent.

The Federal Lower Chamber members may not be re-elected for the immediate following term, although this restriction does not apply to the substitute Lower Chamber members who have never been in office. In this case, they may become holder Lower Chamber members for the immediate following term. However, the holder Lower Chamber members may not be elected for the immediate following term as substitutes.

Election of Lower Chamber Members Through the Principle of Relative Majority

The election of the 300 federal Lower Chamber members through the principle of relative majority is conducted in 300 single-member districts. The distribution of the 300 districts among the thirty-two states is established according to the percentage of the population living in each of them. Based on the results obtained in the population and dwelling census that is carried out every ten years in Mexico, the Constitution establishes that no state may have less than two federal single-member districts.

The most recent redistribution of the 300 districts among the thirty-two states in order to guarantee that each deputy represents an equivalent segment of the population and hence satisfies the principle of equity in the vote, was verified between April 2004 and January 2005, based on the population census carried out in 2000. This new district distribution will be in force until the midterm federal elections of July 2009, and a new district distribution will take place before the presidential and legislative elections of 2012.

The following chart indicates the distribution of the 300 single-member districts in the thirty-two states, resulting from the revision made in 2004 and in force until the midterm elections of 2009.

Election of Lower Chamber Members through the Principle of Proportional Representation

The election of the 200 Lower Chamber members through the principle of proportional representation is carried out by means of regional voters lists in five multi-member districts. 40 Lower Chamber members are equally elected in each of these districts.

In order to participate in the Lower Chamber member’s election, a political party must demonstrate that it has registered candidates for Lower Chamber seats to be elected through the principle of relative majority in at least 200 of the 300 single-member districts. If it complies with this requirement, the political party may proceed to the registration of its regional list of candidates in the five multi-member districts. These regional lists are closed and blocked, meaning that the order of the candidacies is invariable and none of them may be eliminated.

For a party to be entitled to have members of proportional representation in the Lower Chamber, it must attain at least 2 percent of the total votes cast for these elections. The Constitution establishes that a political party that complies with the two aforementioned requirements shall be allocated a number of proportional representation Lower Chamber members per district according to the percentage of national votes won and considering the provisions regarding the maximum amount of seats that a single party may have (300) and the rule of proportionality in the votes/seats ratio of 8 percent, when applicable.

The electoral legislation details the applicable formulas and procedures to appoint proportional representation Lower Chamber members, considering the different hypotheses or scenarios set forth by the aforementioned provisions.

Composition of the Upper Chamber

The Upper Chamber or Senate is composed by 128 members elected through a segmented system in which a section is elected by a majority formula and another by a proportionality formula. Unlike the Lower Chamber, the two segments operate independently.

Three Senators are elected in each of the thirty-two states. For this purpose, the political parties must register a list with two formulas for their candidates. Two of the seats are allocated through the relative majority principle, that is, they belong to the party that obtained the largest number of votes, and the third one is appointed through the first minority principle, that is, to the party that obtained the second largest amount of votes.

The remaining thirty-two seats are appointed by means of the proportional representation system, according to voter rolls in one single national multi-member district. The law establishes that a pure proportionality formula (natural quotient and higher remainder) must be used for their appointment.

As earlier mentioned, the substitute Lower and Upper Chamber members may be elected for the immediate following term as holder members, provided that they had never been in office, but holder Upper and Lower Chamber members may not be elected as substitutes for the immediate following term.

3. Installation and Sessions of the Congress

The Constitution establishes that the Chambers may not open their sessions nor exercise their duties without the presence of more than half of their total number of members. However, the members who are present must meet on the day appointed by law and compel the absentees to be present within the next thirty days. If the absentees fail to attend again, they are considered to have resigned to their office, and the substitutes are summoned. The substitutes must show up within the next 30 days. If they fail to do so, their seats are then considered vacant and new elections are summoned.

The Congress must hold two ordinary session periods per year. The first one begins on September 1 every year and may extend until December 15 of the same year, except in the years where the President of the republic takes office. In this case, the sessions may extend until December 31. The second period begins on February 1 and ends on April 30.

During the recess periods, a Standing Commission consisting of 37 members is formed. Nineteen of them are Lower Chamber members, and eighteen are Upper Chamber members, appointed by their respective Chambers on the day before the closing of the ordinary session periods.

The Standing Commission has the exclusive attribution to summon the Congress or one of the Chambers to extraordinary sessions, either on its behalf or by request of the Executive Branch. The vote of two thirds of the members who are present is mandatory in any case.

The President, the Upper and Lower Chamber members of Congress and the state legislative bodies have the exclusive right to pass laws or decrees.

The federal legal system does not acknowledge any kind of semi-direct democracy mechanism such as plebiscite, referendum, citizen’s initiative or the revocation of freely elected representatives.