As mayor of Mexico City, a job she held until June, Claudia Sheinbaum rarely let her attention to detail slip. While being driven to meetings in her Chevy, she’d snap photos of traffic jams or clogged taxi ranks and send them to the city’s mobility chief, Andrés Lajous, asking him to sort them out. She once urged him to visit the site of a planned bus line extension, insisting he had to see it himself to manage the project, Lajous recalls.

Now Sheinbaum, 61, is a top contender to become the next president of Mexico, and the ideological successor to leftist President Andrés Manuel López Obrador, or AMLO. Some view her as Latin America’s Angela Merkel: a politician with the rigorous mind of a scientist. Like Merkel, Sheinbaum holds a Ph.D. (Merkel’s is in quantum chemistry; hers is in energy engineering) and began her career in academia. Not only has she published a raft of scientific papers, she’s contributed to two landmark reports by the United Nations Intergovernmental Panel on Climate Change (IPCC), the world’s premier body of climate science.

During almost five years in city hall, Sheinbaum oversaw the electrification of Mexico City’s buses and covered the huge Central de Abasto food market with solar panels. Her work as a scientist and as a government official make her look like a climate president in the making. But the politics are far from simple.

Mexico, the world’s 11th-biggest oil producer, is the only Group of 20 country with no net-zero emissions target, and climate policy experts say it’s gone backward in recent years. López Obrador has directed billions of dollars to prop up the indebted state-owned oil company, Petróleos Mexicanos (Pemex), seeing it as essential to national sovereignty. His government just opened a refinery in Tabasco state, and it’s tried to dissolve the National Institute for Ecology and Climate Change as an austerity measure. In part because of policy changes that bolstered the national power utility, private investment in renewables has dropped since AMLO took power in 2018.

The technocratic Sheinbaum is a protégé of the president, who’s so popular in Mexico that vendors sell dolls, balloons and mugs with his grinning face. She’s unlikely to deviate from her mentor’s policies as the race gets underway. And it’s not clear she would make climate and clean energy top priorities even if she beats her competitor from a center-right coalition, the entrepreneur Xóchitl Gálvez, next June. (If either wins, Mexico will be led by a woman for the first time.)

When talking to voters, Sheinbaum has tried to pitch herself as a progressive rooted in the populist nationalism of her party, Morena. In Michoacán, a hub for avocado and lime growers, she said, “We are going to keep advancing with renewable energies and with the protection of the environment, but without betraying the people of Mexico.” Sheinbaum declined to comment for this article.

Mexico is the world’s 15th-biggest greenhouse gas emitter, and its emissions are expected to keep rising through 2030, according to Climate Action Tracker. If Sheinbaum were able to reverse that trend, it would be significant in the global fight to rein in climate change.

The main thing standing in the way is politics, says Tony Payan, director of the Center for the United States & Mexico at Rice University’s Baker Institute. “Sheinbaum will be forced to defend current policy or begin to break away from López Obrador, and it will be interesting to see if she’s capable of doing it,” he says.

Luis Zambrano, an ecologist at the National Autonomous University of Mexico, isn’t hopeful. “She’s shown herself to be someone who has always followed the president,” he says. “At some point, she opted for politics, instead of opting for science.”

Oil has long been key to state revenue in Mexico, and Pemex, a major employer, is also an object of national pride. At an event in March right before the anniversary of Mexico’s nationalization of oil production, Sheinbaum spoke carefully when asked about the country’s energy future. “Of course, we all want to contribute to the reduction of greenhouse gases that provoke climate change, and we all want cities that don’t have contaminated air, and that this be done through the production or use of cleaner energies,” she said. “But that doesn’t mean that that has to come before everything else.”

Long before she was running for president, Sheinbaum was a student obsessed with the energy efficiency of wood-burning stoves and lightbulbs. In graduate school she did a research stint at Lawrence Berkeley National Laboratory in California. “I dedicated myself to modeling the consumption of energy in Mexico—how it’s used, what it’s used for and which sources of energy allow you to meet people’s needs,” she recounted at a recent campaign stop with university students in Nuevo León state.

“She has a really keen curiosity, an intense motivation to understand data and trends,” says Lynn Price, a retired Berkeley Lab scientist who’s collaborated with Sheinbaum on papers going back to when they worked together in the 1990s. Even then, Sheinbaum was interested in how data could be applied to public policy, Price says.

Raised in Mexico City by Jewish scientists—her grandparents left Europe for Mexico in the first part of the 20th century—Sheinbaum entered politics full time in 2000, when López Obrador, then mayor of Mexico City, appointed her his environment minister. She was elected leader of Tlalpan, a borough of Mexico City, in 2015 and then mayor of the city in 2018. In that post, she set a goal of planting millions of trees, piloted home rainwater collection and ordered her employees to plug the city’s rampant water leaks. She stepped down in June to seek Morena’s nomination as its presidential candidate. She won it in September.

She has a reputation as an exacting boss. “Everyone I’ve ever talked to who has worked for her says that her principal virtue and her principal defect is micro-management—the obsession for detail, for the technical parts,” says Carlos Pérez Ricart, who teaches international relations at the Center for Research & Teaching in Economics in Mexico City.

Sheinbaum got her share of criticism as mayor from environmentalists who said she prioritized urban growth over conservation. And the problems she would inherit as president are bigger than bus lanes and traffic jams.

Mexico has pledged to cut emissions 35% by 2030. Power generation is Mexico’s largest source of carbon dioxide emissions; about 72% of its power comes from fossil fuels. The government is building a sprawling solar farm near the US border, but analysts say the next president will need to ramp up a lot more clean energy to make a real dent.

The goliath Pemex has a notoriously poor environmental and safety record. Researchers last year reported two enormous methane leaks from one of its offshore fields. Lenders have threatened to cut off investment unless it cleans up its act.

Meanwhile, climate-fueled extreme weather is posing an increasing danger to Mexico’s citizens. Brutally high temperatures have contributed to the deaths of almost 400 people since March and put further stress on the already struggling national grid. Drought conditions regularly affect swathes of the country and leave cities without water. Rising seas have swallowed coastal homes.

Sheinbaum’s rival, Gálvez, has said she can make fast environmental improvements with the help of the private sector. Sheinbaum has insisted progress will be driven by the state.

Other left-leaning leaders in Latin America who have pushed for a greener future haven’t had an easy time. Colombian President Gustavo Petro has campaigned against fossil fuels on the world stage but made few inroads in his plan to boost wind and solar domestically. In Chile, President Gabriel Boric has so far declined to bail out renewables companies that complained they weren’t making any money.

Sheinbaum, in the name of Mexican energy security, could pressure Pemex on methane releases from flaring and argue the gas should be captured for consumption. If she leaned into renewable energy partnerships with the private sector, it wouldn’t necessarily be read as stepping on the toes of the state utility.

“She has the opportunity to be more friendly toward the private sector—to have a less stringent and hostile view on private participation. That would be important for the climate,” says Diego Rivera Rivota, a research associate at the Center on Global Energy Policy at Columbia University. “But bold action comes with trade-offs.”

Middle-income countries such as Mexico must try to expand their economies and improve living standards while also curbing emissions. It’s a tricky issue to navigate for any political leader. “For many developing countries, for the development to happen, there will be some emissions. Over time it can be reduced,” says Joyashree Roy, a professor at Thailand’s Asian Institute for Technology and a lead author of IPCC report chapters on industry to which Sheinbaum contributed. Because Sheinbaum knows what environmentally responsible growth that raises living standards looks like, “she will be able to argue for it,” Roy says.

Nobody’s sure exactly how she would do it. “At the city level, she did interesting things,” says Bernardo Baranda, the Latin America director for the nonprofit Institute for Transportation & Development Policy. “I think she believes in what she’s doing and the ideas of the president. But many people are waiting to hear her own voice, and that’s the great unknown.” ○