MEXICO CITY -- One of the leading opposition contenders for the Mexican presidency in July’s election on Sunday rejected corruption allegations against him, and accused the government of trying to smear his campaign, which is running second in most polls.

Ricardo Anaya, candidate of a right-left coalition, presented the attorney general’s office with a letter denying allegations by rivals that he had benefited from illicit property deals in Queretaro, his home state in central Mexico.

At the center of the dispute is the purchase and sale of real estate in an industrial park in Queretaro between 2014 and 2016. Anaya said the deals were completely legitimate, setting out the various transactions in a video posted on social media.

“Everything I’ve done has been legal, and above all, 100 percent transparent,” Anaya said in the video.

On Wednesday, the attorney general’s office issued a short statement saying that a complaint had been filed last October by an unnamed party about suspected operations involving illicit funds, prompting an investigation to be launched.

The statement did not detail who was involved. However, Anaya said that the investigation targeted his property deal and was an attempt to damage his reputation and help the candidate of the ruling Institutional Revolutionary Party (PRI).

The PRI’s presidential candidate is former finance minister Jose Antonio Meade, but his campaign has struggled to gain traction. Recent polls have shown Meade losing ground to Anaya and the leftist front-runner, Andres Manuel Lopez Obrador.

Tit-for-tat accusations of corruption between the government and the opposition have been intensifying in recent months.

Much of the attention has focused on media investigations showing how federal auditors over several years detected irregularities worth millions of dollars in the accounts of ministries run by Rosario Robles, the minister for agrarian, land and urban development.

Robles has denied any wrongdoing, but the allegations have hurt the PRI, which has long been tainted by corruption.

On Sunday, congressman Jesus Zambrano of the center-left Party of the Democratic Revolution (PRD), which forms part of Anaya’s coalition, urged the finance ministry to explain the irregularities that occurred under Robles’s watch.

The run-up to the election has also been marred by violence, with deadly attacks on several local politicians and activists.

The PRI on Sunday condemned the killing in Guerrero state of Dulce Rebaja Pedro, a contender for the state congress whose body was found near the city of Chilapa, local media said.