Mexico is a federal presidential republic governed under the Constitution of 1917. Claudia Sheinbaum, sworn in on 1 October 2024, is both head of state and head of government, as every Mexican president is: there is no prime minister. Laws are made by the Congress of the Union, a two-chamber legislature of 628 members (a 128-seat Senate and a 500-seat Chamber of Deputies), and the Supreme Court of Justice of the Nation sits at the top of the courts. Power is shared with 31 states and Mexico City, each with its own elected executive and congress. One rule shapes the whole system: a president serves a single six-year term, the sexenio, and can never return to the office.
President Claudia Sheinbaum (since 1 October 2024): one office, two roles
Under Chapter III of Title III of the Constitution, the president holds the "Supreme Executive Power of the Union". That makes the officeholder head of state, head of government and commander-in-chief of the Mexican Armed Forces at the same time. The president appoints the cabinet secretaries who run the federal ministries and sets the national budget proposal that Congress then approves.
Sheinbaum, a physicist by training and a member of the National Regeneration Movement (Morena), won the general election of 2 June 2024 by a margin of more than 33 points over Xóchitl Gálvez. She received about 35.9 million votes, 59.76% of the total, the largest number of votes ever cast for a Mexican candidate, and carried 31 of the 32 federal entities; Aguascalientes was the only one to back Gálvez. She is the first woman to hold the office. Her predecessor, Andrés Manuel López Obrador, who founded Morena and governed from 2018 to 2024, had set the previous record of 30.1 million votes.
The office works from the National Palace, the red tezontle building that fills the entire east side of the Zócalo in central Mexico City and runs more than 200 metres along it. It is the seat of the federal executive and, since 2019, also the president's official residence. Los Pinos, the residence used from 1934, became a cultural space in December 2018.
Article 82 of the Constitution sets the qualifications: a candidate must be a Mexican citizen by birth with at least one Mexican-born parent, be at least 35 years old, have lived in Mexico for at least twenty years, and must not be a minister of any religion. A candidate who has held the presidency even on a caretaker basis is barred for life. The president is elected by simple plurality, with no runoff. If the office falls vacant, Article 84 makes the Secretary of the Interior provisional president until Congress convenes; an early vacancy triggers a fresh election, a late one a substitute chosen by Congress.
The six-year sexenio and the no-re-election rule (since 1917 and 1928)
The single-term rule is the most distinctive feature of Mexican government, and it comes directly from the country's history. Porfirio Díaz held power for most of the period from 1876 to 1911, and his seventh consecutive re-election in 1910 sparked the Mexican Revolution, the armed conflict that ran from 20 November 1910 to 1920. The revolutionary Constitution drafted in Santiago de Querétaro and approved on 5 February 1917 wrote a ban on presidential re-election into the heart of the new state.
The length of the term has changed more than once. It was four years from 1821 until Díaz stretched it to six in 1904; the 1917 Constitution restored four years; and since 1928 it has been fixed at six. When a 2014 amendment allowed mayors, deputies and senators to seek a second consecutive term, the presidency was deliberately left out. A president remains barred even from a non-consecutive return.
The ban did not, for most of the twentieth century, mean competitive politics. The party founded in 1929 by Plutarco Elías Calles, renamed the Institutional Revolutionary Party (PRI) in 1946, won every presidential election for 71 years. All senators belonged to it until 1976 and every state governor until 1989. That era ended on 2 July 2000, when Vicente Fox of the National Action Party (PAN) won with about 43% of the vote. Elections are now run by the National Electoral Institute (INE), an autonomous agency independent of the government; its president since 2023 is Guadalupe Taddei.
The Congress of the Union: 128 senators and 500 deputies
Articles 50 to 79 of the Constitution vest legislative power in the Congress of the Union, which meets in Mexico City. Together the two chambers pass laws, levy taxes, can admit new states and can declare war. Each chamber also has powers of its own: the Senate handles foreign policy, ratifies treaties and confirms presidential appointments, while the Chamber of Deputies has the final word on the federal spending budget.
The Senate of the Republic
The Senate was created on 4 October 1824, abolished in 1857 and restored in 1874. Its 128 senators serve six-year terms, matching the presidential term, and are chosen by a mixed system introduced in the 1990s. In each of the 31 states and in Mexico City, the party or coalition that comes first wins two seats and the runner-up wins one, the so-called "first minority" seat; that accounts for 96 senators. The remaining 32 are elected by proportional representation from national party lists.
The Chamber of Deputies
The lower house has 500 deputies elected every three years by parallel voting. Three hundred are elected in single-member districts by first past the post; the other 200 come from closed party lists in five large regional constituencies. Rules limit distortion: a party needs at least 3% of the vote to win list seats, its share of seats cannot exceed its share of the vote by more than eight points, and no party may hold more than 300 seats. In the 2024 election Sheinbaum's coalition, Sigamos Haciendo Historia (Morena, the Labor Party and the Ecologist Green Party), won 364 of the 500 seats, a two-thirds supermajority large enough to amend the Constitution. In the Senate it initially held 83 of 128 seats, three short of two-thirds, and reached the threshold through defections in August and November 2024.
The Supreme Court under Hugo Aguilar Ortiz: judges elected since 1 June 2025
The judiciary is headed by the Supreme Court of Justice of the Nation, which interprets the Constitution and hears cases of federal jurisdiction. Below it sit the Electoral Tribunal of the Federal Judiciary, collegiate and unitary circuit courts, and district courts. Until 2025 its justices were nominated by the president and confirmed by the Senate.
That changed with the judicial reform promulgated by López Obrador on 15 September 2024, two weeks before he left office. The constitutional amendments, passed by two-thirds majorities in both chambers and ratified by a majority of state legislatures, replaced appointment with popular election. The Supreme Court was cut from eleven justices to nine, each serving a single twelve-year term instead of fifteen years, and ballots list women and men separately to ensure gender parity. The old Council of the Federal Judiciary was replaced by a new Judicial Disciplinary Tribunal.
The first vote took place on 1 June 2025. Mexicans elected the nine Supreme Court justices, members of the Electoral Tribunal and the disciplinary tribunal, 464 circuit magistrates and 386 district judges; the remaining circuit and district posts go to the voters in 2027, which will make Mexico the first country to elect all of its judges. Turnout was about 13%, the lowest in the country's democratic history, and invalid or blank ballots passed 20% of votes cast. Supporters presented the change as a fight against corruption; opposition parties, court workers and international observers warned that it weakened judicial independence. Hugo Aguilar Ortiz, a lawyer of Mixtec heritage from Oaxaca, won the most votes of the 64 candidates and so became president of the court for the 2025–2027 term.
31 states and Mexico City: governors, state congresses and free municipalities
The country's official name, the United Mexican States (Estados Unidos Mexicanos), describes a federation. Each of the 31 states is legally "free and sovereign" in its internal affairs, with its own constitution, an elected governor, a single-chamber state congress and a state court system. States run their own police forces, economic and social development policy and local taxes, provided their laws do not contradict the federal Constitution. Our guide to Mexico’s 31 states lists them all.
Mexico City is a special case. For most of the twentieth century the Federal District was run directly by the president through an appointed regent, a source of long resentment among its residents. Its head of government has been elected since 1997, and on 29 January 2016 the city became a federal entity with status equivalent to a state, though it is still not formally one. The head of government has the rank of a governor and serves a six-year term that runs alongside the president's. The current holder is Clara Brugada of Morena, the former mayor of the Iztapalapa borough, who won the 2024 election. The capital is divided into 16 boroughs rather than municipalities.
Below the states sit the municipalities, 2,462 of them according to the list of states maintained on Wikipedia. The principle of the municipio libre, the free municipality, is another legacy of the Revolution: each elects its own council headed by a municipal president, chosen every three years.
The 1917 Querétaro Constitution: what it guarantees and how it changes
The Political Constitution of the United Mexican States succeeded the Constitution of 1857 and is often described as the legal triumph of the Revolution. It was the first constitution anywhere to set out social rights, ahead of the Soviet Russian constitution of 1918 and Germany's Weimar constitution of 1919. Three articles carry most of that weight: Article 3 made education free, compulsory and secular; Article 27 laid the basis for land reform and national ownership of subsoil resources; and Article 123 protected workers.
The text has been amended many times, and not always in one direction. Strict limits on the Catholic Church in Articles 3, 5, 24, 27 and 130, which President Calles tried to enforce in 1926 and which led to the Cristero War, were largely repealed in 1992 under Carlos Salinas de Gortari. The same 1992 revision rewrote Article 27 to allow the privatisation of communal ejido land. Amendments require two-thirds of both chambers of Congress plus approval by a majority of the state legislatures, which is why the 2024 supermajority mattered so much: it allowed the judicial overhaul to pass within weeks. Constitution Day, marking 5 February 1917, is a national holiday held on the first Monday of February. For the money that these institutions tax and spend, see our guide to the Mexican peso.