“This won’t earn the president credibility, that the commission is in the hands of somebody who is close to him,” said María Amparo Casar, an anti-corruption expert at the Mexican Institute for Competitiveness.

Mr. Peña Nieto also outlined a series of bureaucratic measures that he said would help reduce corruption, including a requirement that top officials reveal any conflict of interest to the comptroller. But Ms. Casar said they were not convincing: “It falls short of what people are demanding,” she said.

Still, Ms. Casar said the appointment of a new comptroller was a positive sign because the position, at the top of the ministry of public function, had been vacant for two years. The intent had been to replace part of the agency’s functions with an anti-corruption prosecutor, but no one was ever appointed.

The real test of the president’s commitment to combating corruption, she said, will be in the details of anti-corruption legislation expected to be sent to congress soon.

Attacking corruption “is not in their DNA,” she said of Mr. Peña Nieto’s administration. “But I hope they won’t be so insensitive as to not take the public pulse on corruption.”

Ms. Rivera, the president’s wife, later said she would sell the property, which she was buying on credit from Grupo Higa. The bullet train contract was initially canceled and then put up for bid again before it fell to budget cuts last week.

Grupo Higa also sold a house on a golf course in the rural retreat of Malinalco to Mr. Videgaray in 2012, just before he took office. Mr. Videgaray received a mortgage from Grupo Higa but told reporters that he had paid it off at the beginning of last year.