Cuauhtémoc Cárdenas Solórzano, a towering figure of the Mexican left whose challenge to a once long-ruling party helped propel the country toward democracy, has died. He was 92.

His death was confirmed by President Claudia Sheinbaum. A three-time presidential candidate, Cárdenas led a rebellion within the once dominant Institutional Revolutionary Party, or PRI, which governed Mexico for most of the 20th century. The revolt grew into a broad political and social movement that helped break the party’s grip on power and fostered the creation of other parties and democratic institutions that endure today.

Sheinbaum hailed Cárdenas as “a man of firm principles who transformed the country’s political life,” according to a post on X on Wednesday. “His role in Mexico’s contemporary history is fundamental.”Cárdenas was a staunch defender of the state’s role in strategic areas of public life, particularly Mexico’s oil industry, which was nationalized in 1938 under his father, President Lázaro Cárdenas del Río. His progressive vision became a cornerstone of Mexico’s modern left and influenced generations of politicians, including Sheinbaum and former President Andrés Manuel López Obrador.

Cárdenas was born in Mexico City on May 1, 1934. His father became president later that year and would champion sweeping land reforms, and pro-immigration policies that welcomed scores of refugees who fled the Spanish Civil War.

The younger Cárdenas studied civil engineering at the National Autonomous University of Mexico, before he became involved in left-wing political organizations early in his career. He eventually joined the PRI, the party that dominated Mexican politics for more than seven decades.

After holding several public posts, Cárdenas served as governor of the western state of Michoacan from 1980 to 1986. From there, he helped organize a dissident movement within the PRI that demanded more democratic procedures for selecting candidates.

The rupture became irreversible in 1988, when the PRI selected Carlos Salinas de Gortari as its presidential candidate over Cárdenas, who wanted the party’s choice to be made democratically. Cárdenas broke with the party and became the candidate of the National Democratic Front, a coalition of leftist and opposition groups.

He officially lost the election to Salinas in a result that was clouded by allegations of fraud — fueled by the collapse of the vote counting system on election night and widespread doubts about the official tally. The political upheaval surrounding the contest contributed to reforms that eventually produced an autonomous electoral authority and more competitive elections.

Cárdenas unsuccessfully ran for president twice more, in 1994 and 2000. The 2000 election finally ended the PRI’s uninterrupted hold on the presidency, although it was conservative candidate Vicente Fox who achieved the historic victory.

Cárdenas nonetheless secured a breakthrough of his own in 1997, when he won the first election for head of government of Mexico City, a position equivalent to mayor. It was the Mexican left’s most important electoral victory up to that point and established the capital as its strongest political base. Every elected government of Mexico City since then has been led by the left.

For years, Cárdenas was regarded as the moral leader of the movement. His influence gradually receded with the rise of López Obrador, who founded a rival leftist party, Morena, and won the presidency in 2018.

Yet Cárdenas’s place in Mexican history remained distinct: he challenged an entrenched political system, gave the democratic opposition a national voice and helped lay the groundwork for the transfer of power that transformed the country.