MEXICO CITY — After his landslide victory last year, President Andrés Manuel López Obrador of Mexico promised a staggering transformation of his country — on par with independence from Spain and the Mexican Revolution.

But five months into his term, the new Mexico he says he is building looks an awful lot like the old one he swore to leave behind.

Corruption was a hallmark issue for Mr. López Obrador during the campaign, a national scourge he vowed to end. Yet his government has announced no major prosecutions of public officials or other prominent figures on corruption charges since he took office.

Beyond that, in his first three months, his government awarded more than 70 percent of its contracts directly, without competitive bids, according to Mexicans Against Corruption and Impunity, an anticorruption group — a sharp reversal from Mr. López Obrador’s promise to break with that tradition.