# Congress of the Union

The Congress of the Union (Spanish: Congreso de la Unión, pronounced), formally known as the General Congress of the United Mexican States (Congreso General de los Estados Unidos Mexicanos), is the legislature of the federal government of Mexico. It consists of two chambers: the Senate of the Republic and the Chamber of Deputies. Its 628 members (128 senators and 500 deputies) meet in Mexico City.

## Structure

The Congress is a bicameral body, consisting of two chambers: the Senate of the Republic and the Chamber of Deputies. Its structure and responsibilities are defined in the Third Title, Second Chapter, Articles 50 to 79 of the 1917 Constitution. The upper chamber is the Senate, Cámara de Senadores or Senado. It comprises 128 seats: 96 members are elected by plurality vote, with three members being elected in each state (two seats are awarded to the winning party or coalition and one to the first runner-up); the other 32 members are elected by proportional representation in a single country-wide constituency. Senators serve six-year terms.
The lower house is the Chamber of Deputies, or Cámara de Diputados. It has 500 seats; 300 members are elected by plurality vote and the other 200 members are elected according to proportional representation (PR), through a system of regional lists (one for each of the five constituencies established for the election by law). Deputies serve three-year terms.
The 200 PR seats are distributed generally without taking into account the 300 plurality seats (parallel voting). Since 1996, however, a party cannot get more seats overall than 8% above its result for the PR seats (a party must win 42% of the votes for the PR seats to achieve an overall majority).
There are two exceptions to that rule. A party can lose only PR seats by that rule (not plurality seats). Also, a party cannot get more than 300 seats overall (even if it has more than 52% of the votes for the PR seats).

## Powers

The powers invested in Congress are defined in article 73 of the Constitution. Among its powers, Congress can admit new States into the Union, alter the allocation of powers granted to the federal government, lay and collect taxes, declare war (upon request of the Government), provide for and maintain the Union's armed forces, and coordinate economic activities.
Article 74, 75 and 76 of the Constitution state that each Chamber can address specific matters. In fact, some powers are reserved either to the Chamber of Deputies or to the Chamber of Senators, making the Congress of the Union an example of imperfect bicameralism. For example, the former can approve the federal budget submitted by the Government, while the latter has the power to analyze the foreign policy of the Government, approve or dismiss the Presidential nominations of the Attorney General, Supreme Court Justices, diplomatic agents, general consuls, and senior civil and military officials.

## Permanent Committee

The Comisión Permanente del Congreso de la Unión, translated variously as the Permanent Committee or Standing Committee, is a body of 19 deputies and 18 senators that is responsible for tasks relating to the Congress when it is in recess.

## Term

It is conventional to refer to each Legislature by the Roman numeral of its term. Thus, the current Congress (whose term lasts from 2024 to 2027) is known as the "LXVI Legislature"; the previous Congress (whose term lasted from 2018 to 2021) was the "LXIV Legislature", and so forth. The I Legislature of Congress was the one that met right after the Constituent Congress that enacted the 1857 Constitution.
Early in the 20th century, the revolutionary leader Francisco I. Madero popularized the slogan Sufragio Efectivo – no Reelección ("Effective suffrage, no reelection"). In keeping with that long-held principle, and until 2014, the 1917 Constitution stated that "Deputies and Senators could not be reelected for the next immediate term".

### Reelection

On February 10, 2014, Article 59 of the Mexican Constitution was amended to allow reelection to the legislative bodies for the first time. Starting with the general election of 2018, deputies and senators are allowed to run for reelection. Members of the Chamber of Deputies may serve up to four terms of three years each while members of the Senate may serve two terms of six years each; in total, members of both houses will be allowed to remain in office for a total of 12 years.

## Last election
### Senate

| Party or alliance | Party or alliance | Party or alliance | Party or alliance | Votes | % | Seats | Votes | % | Seats | Total seats | +/– |
| | Sigamos Haciendo Historia | | National Regeneration Movement | 7,526,453 | 13.19 | 21 | 24,484,943 | 42.48 | 14 | 60 | +5 |
| | Sigamos Haciendo Historia | | Ecologist Green Party of Mexico | 2,298,726 | 4.03 | 4 | 5,357,959 | 9.30 | 3 | 14 | +8 |
| | Sigamos Haciendo Historia | | Labor Party | 1,215,172 | 2.13 | 0 | 3,214,708 | 5.58 | 2 | 9 | +3 |
| | Sigamos Haciendo Historia | | Common candidates | 21,731,737 | 38.08 | 39 | | | | – | – |
| | Sigamos Haciendo Historia | Total | Total | 32,772,088 | 57.43 | 64 | 33,057,610 | 57.36 | 19 | 83 | +14 |
| | Fuerza y Corazón por México | | National Action Party | 1,148,920 | 2.01 | 1 | 10,107,537 | 17.54 | 6 | 22 | –1 |
| | Fuerza y Corazón por México | | Institutional Revolutionary Party | 316,636 | 0.55 | 0 | 6,530,305 | 11.33 | 4 | 16 | +2 |
| | Fuerza y Corazón por México | | Party of the Democratic Revolution | 76,082 | 0.13 | 0 | 1,363,012 | 2.36 | 0 | 2 | –6 |
| | Fuerza y Corazón por México | | Common candidates | 16,244,373 | 28.47 | 29 | | | | – | – |
| | Fuerza y Corazón por México | Total | Total | 17,786,011 | 31.17 | 30 | 18,000,854 | 31.23 | 10 | 40 | +2 |
| | Citizens' Movement | Citizens' Movement | Citizens' Movement | 6,460,220 | 11.32 | 2 | 6,528,238 | 11.33 | 3 | 5 | –2 |
| Non-registered candidates | Non-registered candidates | Non-registered candidates | Non-registered candidates | 46,230 | 0.08 | 0 | 47,092 | 0.08 | 0 | 0 | 0 |
| Total | Total | Total | Total | 57,064,549 | 100.00 | 96 | 57,633,794 | 100.00 | 32 | 128 | 0 |
| Valid votes | Valid votes | Valid votes | Valid votes | 57,064,549 | 96.08 | | 57,633,794 | 96.05 | | | |
| Invalid/blank votes | Invalid/blank votes | Invalid/blank votes | Invalid/blank votes | 2,326,742 | 3.92 | | 2,369,932 | 3.95 | | | |
| Total votes | Total votes | Total votes | Total votes | 59,391,291 | 100.00 | | 60,003,726 | 100.00 | | | |
| Source: INE (PR) ||||||||||||

### Chamber of Deputies

| Party or alliance | Party or alliance | Party or alliance | Party or alliance | Votes | % | Seats | Votes | % | Seats | Total seats | +/– |
| | Sigamos Haciendo Historia | | National Regeneration Movement | 3,686,979 | 6.48 | 37 | 24,286,317 | 42.40 | 75 | 236 | +38 |
| | Sigamos Haciendo Historia | | Ecologist Green Party of Mexico | 676,092 | 1.19 | 0 | 4,993,988 | 8.72 | 20 | 77 | +34 |
| | Sigamos Haciendo Historia | | Labor Party | 507,604 | 0.89 | 0 | 3,254,718 | 5.68 | 13 | 51 | +14 |
| | Sigamos Haciendo Historia | | Common candidates | 27,446,014 | 48.26 | 219 | | | | – | – |
| | Sigamos Haciendo Historia | Total | Total | 32,316,689 | 56.82 | 256 | 32,535,023 | 56.80 | 108 | 364 | +86 |
| | Fuerza y Corazón por México | | National Action Party | 372,670 | 0.66 | 3 | 10,049,375 | 17.55 | 40 | 72 | –42 |
| | Fuerza y Corazón por México | | Institutional Revolutionary Party | 101,574 | 0.18 | 0 | 6,623,796 | 11.56 | 26 | 35 | –35 |
| | Fuerza y Corazón por México | | Party of the Democratic Revolution | 20,374 | 0.04 | 0 | 1,449,660 | 2.53 | 0 | 1 | –14 |
| | Fuerza y Corazón por México | | Common candidates | 17,493,425 | 30.76 | 39 | | | | – | – |
| | Fuerza y Corazón por México | Total | Total | 17,988,043 | 31.63 | 42 | 18,122,831 | 31.64 | 66 | 108 | –91 |
| | Citizens' Movement | Citizens' Movement | Citizens' Movement | 6,446,537 | 11.34 | 1 | 6,497,404 | 11.34 | 26 | 27 | +4 |
| | Independents | Independents | Independents | 72,012 | 0.13 | 1 | 72,012 | 0.13 | 0 | 1 | +1 |
| Non-registered candidates | Non-registered candidates | Non-registered candidates | Non-registered candidates | 48,871 | 0.09 | 0 | 49,329 | 0.09 | 0 | 0 | 0 |
| Total | Total | Total | Total | 56,872,152 | 100.00 | 300 | 57,276,599 | 100.00 | 200 | 500 | 0 |
| Valid votes | Valid votes | Valid votes | Valid votes | 56,872,152 | 96.34 | | 57,276,599 | 96.32 | | | |
| Invalid/blank votes | Invalid/blank votes | Invalid/blank votes | Invalid/blank votes | 2,162,171 | 3.66 | | 2,189,869 | 3.68 | | | |
| Total votes | Total votes | Total votes | Total votes | 59,034,323 | 100.00 | | 59,466,468 | 100.00 | | | |
| Source: INE (PR) ||||||||||||