The dramatic collapse of a rail overpass in Mexico City that killed at least 24 people has dealt a blow to two of President Andrés Manuel López Obrador's most senior aides, who are widely viewed as the leading candidates to succeed him.
Monday night's accident has stirred up concern about the city's infrastructure, in particular Linea 12, the metro line where the collapse occurred, and a flagship project of Foreign Minister Marcelo Ebrard when he was mayor from 2006 to 2012. Ebrard's name is strongly associated with Linea 12.
Its problems have also become a headache for the city's current mayor, Claudia Sheinbaum, who has taken flak for other accidents in the metro system since she took office 2-1/2 years ago.
Since opening in 2012, Linea 12 has had a troubled history, suffering disruptions and closures due to technical flaws, as well as allegations of corruption over its construction.
At a Tuesday morning news conference with Lopez Obrador, reporters called on both Ebrard and Sheinbaum to explain how the metro line could have been so unsound, citing complaints and warnings from the public in advance of the disaster.
Both politicians said a thorough investigation should be conducted, and urged people to await the findings.
"Whoever acts with integrity should fear nothing," said Ebrard, who has consistently rejected the notion there was any wrongdoing in the building of Linea 12, which he inaugurated in late October 2012, a month before his term as mayor ended.
When asked if he was worried that he would be blamed for the accident, Ebrard noted the completed project was only "definitively delivered" to the Mexico City government in July 2013, several months after he had left office.
Sheinbaum, in a later news conference, suggested a structural problem had likely caused the collapse, and drew attention to the fact that Linea 12 had a "history."
"The issue here is who is responsible," she said, when asked if the head of the metro system should be fired.
Political pundits regard Ebrard and Sheinbaum as the main rivals to succeed Lopez Obrador when his term ends in late 2024, although neither has publicly declared they will be candidates. Lopez Obrador is constitutionally barred from running.
A spokesman for Ebrard said he was not thinking about 2024, and that his priority was that the victims be looked after and for an independent investigation to be carried out to establish what had triggered the collapse.
Sheinbaum's office declined to comment.
Riding high in the polls as he nears the half-way point of his term, Lopez Obrador has sought to reduce lucrative contracts for big business, but also pressed aides to tighten their belts, fueling criticism that he has hurt public services.
Perhaps the most powerful figure in the administration after the president, Ebrard is viewed as a political moderate to the right of Lopez Obrador. Sheinbaum is seen as closer to the president, who often seeks to underline his bond with her.
The accident occurred a few weeks before nationwide elections on June 6 that will determine who controls the lower house of Congress. Lopez Obrador's National Regeneration Movement (MORENA) is heavily favored to come out on top.
While it was unclear if the accident would have any major electoral impact, it could erode confidence in MORENA in the capital area, said Federico Berrueto, director general of polling firm GCE.
Mexico City has been dominated by Lopez Obrador's political machinery since he first won election as mayor in 2000.
Problems will grow for the government if the metro accident becomes seen as an example of its incompetence, Berrueto said.
A GCE telephone poll of 401 city residents after the accident showed that some 22% of them spontaneously said the main responsibility lay with Ebrard, while 4.5% picked Sheinbaum.
Another 17% blamed either the current head of the metro, the city government, or those in charge of maintenance. Just over one in four people pointed the finger at the companies who built the line, while the federal government was singled out by 3.3%.
Ramon Pedraza, a 53-year-old who lives near the station where the track came down, criticized Ebrard, accusing him of cutting corners to finish Linea 12. Ebrard has always rejected such accusations.
If the blame sticks to the government, it could spell trouble for Ebrard and Sheinbaum, said Fernando Belaunzaran, an opposition politician from Mexico City and former party colleague of the two.
"If the problem was structural, it hits Marcelo. If the problem was maintenance, it hits Sheinbaum," he said. "The struggle over succession will be about trying to demarcate the responsibility."