MEXICO CITY (AP) — Cuauhtémoc Cárdenas, a three-time presidential candidate and one of Mexico's most important modern political voices, died Wednesday at 92, Mexican President Claudia Sheinbaum said.

An undisputed leader of the Mexican left, Cárdenas was the son of one of the country’s most popular presidents — Gen. Lázaro Cárdenas. He was respected by allies and critics alike.

Cárdenas played a pivotal role in Mexico’s democratization, beginning with his first presidential bid in 1988, which ended in a defeat widely regarded as the result of massive electoral fraud.

He became Mexico City’s first popularly elected mayor in 1997. Cárdenas was so steadfast in his principles that in 2014 he resigned from the party he had founded in the late 1980s, the Democratic Revolution Party, because it governed the state of Guerrero when 43 students disappeared.

Cárdenas also distanced himself from his longtime ally Andrés Manuel López Obrador when López Obrador became president in 2018.

Cárdenas was “a man of firm principles,” Sheinbaum said on X, who transformed Mexico’s political life by leading “a peaceful democratic movement that channeled millions of Mexicans’ yearning for change.”

“That historic election day, when he should have been recognized as president, marked the beginning of the democratic transformation. His dignity and republican convictions remain an essential reference point for our nation," she added.

Cárdenas, a civil engineer by training, was the son of President Lázaro Cárdenas, who nationalized the oil industry in 1938 and opened Mexico to refugees from the Spanish Civil War.

The younger Cárdenas began his political career with the Institutional Revolutionary Party, better known as the PRI, and served as a senator and later as governor of the western state of Michoacán. In the late 1980s, he began leading a democratic faction within that party, from which he eventually broke away completely following electoral fraud.

Together with other politicians, he founded the PRD in 1989 and ran as its presidential candidate in 1994 and 2000.

Cárdenas ran for president again in 1994 and lost. In 1997, however, he became the first elected mayor of Mexico City, and in 2000 he once again ran for president and failed for a third time.

The death was met by a swell of grief, including from former Mexican leaders across the political spectrum.

Former Mexican President Vicente Fox (2000-2006) wrote that “we were political adversaries but something bigger united us: the conviction that Mexico deserved complete democracy.”

Sheinbaum’s predecessor and ally López Obrador (2018-2024) called him a “pioneer of the democratic movement.”

“Without him, the country’s political reality would be different. He was a transformative figure; he leaves us his teachings and ideals that never die,” López Obrador wrote on a post on X.