The front-runner is Claudia Sheinbaum, 61, a former mayor of Mexico City, who holds a double-digit lead in polls over rival Xóchitl Gálvez. Sheinbaum is promising to continue the programs of President Andrés Manuel López Obrador, founder of the Morena party and a longtime icon of the left. (He’s constitutionally barred from reelection).

Here’s an introduction to the presidential contenders. Voters on Sunday will also choose a new Congress, the Mexico City mayor, eight governors and more than 20,000 local officials in Mexico’s 31 states and the capital.

Sheinbaum grew up in Mexico City, the daughter of two leftist scientists. The family was close to Raúl Álvarez Garín, a leader of the 1968 pro-democracy protests that were brutally suppressed by security forces. As a girl, Sheinbaum joined her parents in taking food to him in prison, she said in an interview for the book “Claudia Sheinbaum: Presidenta.”

Disciplined and driven, Sheinbaum followed her mother, biologist Annie Pardo, into science. Sheinbaum earned a PhD in electrical engineering at the National Autonomous University of Mexico, or UNAM, a traditional training ground for Mexican leaders, and conducted doctoral research at the University of California at Berkeley for several years in the 1990s.

She has published dozens of academic articles on energy, the environment and sustainable development, and contributed to reports of the Intergovernmental Panel on Climate Change, which won the Nobel Peace Prize in 2007.

If elected, Sheinbaum would be the first Jewish head of state in predominantly Catholic Mexico. She’s recalled celebrating holidays such as Yom Kippur with her grandparents, who fled discrimination and Nazi persecution in their native Bulgaria and Lithuania. But she is not personally religious.

As a student, Sheinbaum plunged into university politics, helping organize a successful strike at the UNAM in 1987 against an increase in fees and a tightening of entrance requirements. She married a leader of the student movement, Carlos Imaz, and their home became a meeting place for leftist politicians. One of them, López Obrador, became mayor of Mexico City in 2000, as the country completed its transition from a one-party, authoritarian state to democracy. He invited Sheinbaum to be his environment secretary.

In 2004, scandal shook Sheinbaum’s family when a video emerged showing her husband, then a Mexico City official, receiving a bag of cash from a businessman linked to corruption. Imaz was accused of violating the electoral law, but later exonerated. The couple eventually divorced.

In 2015, Sheinbaum became borough president of Tlalpan, in southern Mexico City. Three years later, as López Obrador won the presidency, she was elected mayor of the capital. She is known as a meticulous problem-solver, and a low-key but fiercely loyal disciple of the president.

Sheinbaum has promised to follow López Obrador’s policies of increasing aid to poorer Mexicans and consolidating the government’s role in the energy sector. But she wants to reorient the country toward renewable energy, and rely more on the police and national guard — rather than the army — to reduce violence and crime.

Sheinbaum and Imaz raised two children; one is an academic who lives in the United States, the other an artist. In November, Sheinbaum married a friend from her college days, Jesús María Tarriba, an economic risk analyst.

Gálvez, 61, represents a coalition of opposition parties from the center-right and center-left. She’s a plain-talking business executive who has pursued her political career in the conservative National Action Party, or PAN.

Gálvez grew up in a rural town in the central state of Hidalgo, the daughter of an Otomí Indigenous father and a mixed-race mother. She has made her life story the central narrative of her campaign. As a girl, Gálvez sold jello cups and tamales on the street to support her family. She says her father, a schoolteacher, drank heavily and abused her stay-at-home mother. (Both have since died.)

At 16, Gálvez moved by herself to Mexico City, where she rented an attic apartment in a working-class neighborhood and found work as a telephone operator. She was soon admitted to the UNAM, and studied computer engineering.

Gálvez founded two tech companies that contribute to the design and maintenance of “intelligent” energy-efficient buildings.

In 2000, newly elected President Vicente Fox, of the PAN, named her to head a federal commission that oversees Indigenous affairs. She was eventually elected leader of the Miguel Hidalgo borough of Mexico City, and in 2018, a member of the Mexican Senate.

Gálvez is known for wearing traditional Indigenous dresses and traveling around Mexico City on a bike. In June 2023, she seized the spotlight by appearing at the presidential palace and demanding to be admitted to López Obrador’s daily morning news conference. She wanted to rebut his charges that she favored eliminating government pensions for the elderly.

He refused her entry. That touched off a war of words that made Gálvez famous, celebrated for her witty, sometimes off-color ripostes. She has portrayed herself as unafraid of the powerful president, a woman with the “ovaries” to stand up to organized crime.

She’s campaigned on tackling crime, strengthening government watchdog institutions created during the democratic transition, bolstering ties with the United States and attracting more companies to near-shore their production closer to the U.S. market.

Gálvez and her longtime partner, the business executive turned-musician Rubén Sánchez, have two adult children.

Máynez, 38, is a long-shot candidate, representing a small but growing party called the Citizens’ Movement. The federal deputy has focused his campaign on the youth vote, portraying himself as the only candidate who can change “old-style Mexican politics.”

Máynez grew up in the northern state of Zacatecas and earned a degree in international relations from a Jesuit university, the Institute of Technology and Higher Studies of the West. At 25, he became a state lawmaker for the long-ruling Institutional Revolutionary Party, or PRI. Three years later, he resigned from the PRI and joined the centrist Citizens’ Movement.

He jumped into the presidential race in January after the withdrawal of the party’s most popular presidential candidate, Samuel García, the governor of the northern state of Nuevo León.

Máynez says he would reduce the country’s reliance on the military to fight organized crime, establish a legal, regulated market for marijuana, and shift the state-owned oil and electricity companies toward renewable energy.

Rios reported from Monterrey, Mexico. Gabriela Martinez contributed to this report.