MEXICO CITY >> The votes are still being counted, but this much is clear: Mexico’s leftist governing party dominated Sunday’s elections.

Claudia Sheinbaum, the first woman and first Jewish person to be elected president of Mexico, beat her opponent Sunday by a stunning 30 percentage points or more, early returns show. She and her Morena party were expected to win, but they outperformed preelection polls: She won a larger share of the vote than any presidential candidate in decades, and her party and its allies are within reach of claiming big enough majorities in Congress to enact constitutional changes that have alarmed the opposition.

Preliminary results show Morena taking seven of the nine governorships up for grabs — including the most prominent, Mexico City’s — and winning supermajorities in at least 22 of the 32 state legislatures.

The election served as a referendum on the nearly six-year term of Andrés Manuel López Obrador, the current president, reflecting that a solid majority of the electorate has endorsed his stewardship of the country.

“We’re taking the whole shebang in these elections,” Mario Delgado, head of the Morena party, said in a speech Sunday.

Unrestrained ambitions

During López Obrador’s tenure, millions of people were brought out of poverty, the minimum wage doubled and pensions became available to many more Mexicans. But he also empowered the military, prioritized fossil fuels and pushed measures that critics say could weaken Mexico’s democratic institutions.

Still, concerns over such moves did little to sway most voters from supporting Sheinbaum, who is López Obrador’s protege, and their party.

“Voters gave Claudia a mandate that only a very few dared to predict,” said John Feeley, former deputy chief of mission at the U.S. Embassy in Mexico from 2009 to 2012. “Claudia cleaned house.”

For some critics, though, the ascent of a Morena party in much tighter control of both houses of Congress has already raised alarms. They warn that with supermajorities, the party could advance contentious legislation championed by López Obrador, potentially dismantling crucial checks on presidential power.

“I had ruled out the possibility that Morena would have a blank check to do whatever they wanted. But that’s what we’re seeing now,” said Roberta Lajous, a Mexican diplomat who served as the country’s ambassador to four countries. “The democratic system has been used to limit democracy.”

The systemic changes López Obrador has proposed would, among other things, reduce the number of legislators in Congress; eliminate many independent regulators, transferring their functions to federal agencies; and make Supreme Court justices subject to election by popular vote. He is also seeking to make electoral officials chosen by popular vote, a measure that critics warn would weaken their independence.

The opposition in Congress had thwarted those ambitions — until now.

“There seems to be a consensus of a large part of the population to say, ‘Go ahead with your project,’” said Sergio López Ayllón, a law professor at the National Autonomous University of Mexico who has advised institutions such as the Mexican Senate and the Supreme Court.

One unknown is how committed Sheinbaum, who will take office Oct. 1, really is to pushing through the changes López Obrador introduced in February, and which she quickly adopted as her own. Although she has defended the proposals publicly, analysts have also said she had no choice but to wholly back López Obrador on the campaign trail.

Electoral officials are expected to announce the final results of the election sometime this week.

Worry in the markets

The Mexican peso fell more than 3% on Monday, a rare decline for a currency that has recently remained strong against the dollar. The jitters in financial markets reflect broader unease over a potential erosion of checks and balances, which could expand the government’s role in the economy, according to financial strategists.

A major concern for businesses is the potential “election of judges up through the Supreme Court and the virtual gutting of the independence of regulators,” said Roberta Jacobson, a former U.S. ambassador to Mexico. The move, she said, could affect companies’ ability to get a fair hearing on disputes, with either regulators or the judiciary.

“What you are doing is keeping those bodies, but taking away any fig leaf of independence by putting their functions into the executive branch,” Jacobson said of regulators. “This would take any pretense of independence away and vest that power into the presidency.”

Sheinbaum has signaled openness to working with the private sector, saying in a speech to supporters Monday morning, “We will respect business freedom and honestly promote and facilitate domestic and foreign private investment.”

It’s possible she makes the measures a priority “given the importance of this to López Obrador’s project and legacy,” Jacobson said. But, she added: “The other possibility is that she lets it languish without ever pushing for a vote.”

Yet another scenario is raising anxiety among the government’s detractors. The new Congress will briefly overlap in September with the last month of López Obrador’s term, giving him a chance to push through structural changes if the ruling party secures a supermajority in the Senate.