Sheinbaum, a 61-year-old scientist who served as mayor of Mexico City from 2018 to 2023, has the support of outgoing President Andrés Manuel López Obrador.
López Obrador, in power since 2018, cannot run for the top job again because Mexico's constitution limits presidential terms to a single six-year term.
Recent polls show his approval rating near 60%. As a popular leader, he instead channeled his influence to Ms. Shane Baum, a member of his Morena party.
Many of the promises President López Obrador made when he took office have yet to be fulfilled, but his efforts to reduce poverty and help older Mexicans have made him popular with beneficiaries of these social programs.
Winning the president's endorsement may have broadened Sheinbaum's voter base significantly, but it also raised questions about how independent she is from the sometimes overwhelming leader.
Ms. Sheinbaum promised to continue to build on Ms. López Obrador's many achievements while emphasizing that she is her own woman.
Their political party, Morena, boasts how millions of Mexicans have been lifted out of poverty in the past six years.
Morena says policies such as more than doubling the minimum wage are reducing the number of people living in poverty.
But economists say other factors are also at play, including an increase in remittances sent by Mexicans living abroad to friends and family back home.
