MEXICO CITY (AP) — A group of influential Mexican intellectuals and writers penned an open letter to President Enrique Pena Nieto, asking him to either bring charges or drop what is widely seen as a politicized investigation of an opposition presidential candidate.

In a letter posted Sunday, the group said prosecutors' attempts to pursue a money-laundering investigation against an alleged associate of candidate Ricardo Anaya "have further eroded the authority of the institutions that make up Mexican government."

The letter was signed by former government officials like Jorge Castaneda and Arturo Sarukhan and intellectuals including Jose Woldenberg and Enrique Krauze. The group stressed they weren't supporting Anaya — just asking authorities not to politicize law enforcement.

"If there is firm evidence of any offense committed by Ricardo Anaya, we demand judicial authorities act on that," the letter said. "But if that is not the case, the use of the Attorney General's Office to persecute an opposition leader puts Mexico on the same level as authoritarian regimes."

Anaya, the candidate of the conservative National Action Party, is running second in polls for the July 1 presidential race behind leftist Andres Manuel Lopez Obrador. The candidate of Pena Nieto's Institutional Revolutionary Party, Jose Antonio Meade, is in third.

Last week, the Attorney General's Office posted a CCTV tape of Anaya entering the office's headquarters in Mexico City along with his lawyers and supporters. The tape is unremarkable, though someone in the group is heard uttering a curse.

Acting Attorney General Alberto Elias Beltran appeared to release the tape precisely because authorities wanted people to hear the swearing.

"There were insults against the employees of the Attorney General's Office," Beltran said later in explaining the video.

Anaya and the others seemed unaware they were being recorded. Taping lawyer-client meetings, or having people taped by a third party without their consent, is prohibited in Mexico.

The money-laundering probe focuses on an associate of Anaya who had questionable business dealings after he invested in a real estate project in which the candidate was involved. Anaya has said he had no responsibility for what others did with the money after the real estate was sold.

Anaya has claimed the entire investigation is a politically driven campaign by the government to discredit him and breathe life into the candidacy of Meade.

"The administration of Enrique Pena Nieto has launched a brutal attack on me aimed at knocking me out of the presidential race through the illegal and partisan use of government institutions like the Attorney General's Office," Anaya said Sunday. He called it "a serious threat to our democracy."

Pena Nieto appeared to try to down play the scandal Monday, telling local media, "This is the kind of he-said, she-said among candidates that is a normal part of every election campaign."

"It seems to me that this is a natural climate of any election campaign," the president said.

Meade, for his part, said Monday that Anaya made "bad economic decisions" and should be prepared as a candidate to "shoulder the consequences."

"I think that in a serious contest, in a relevant contest, we who are seeking and aspiring (to office) must be serious, consistent and congruent. ... Ricardo was enriched, and the evidence of that enrichment is there today for all to see, and that is what we should be talking about," Meade said.

The investigation comes as prosecutors appear to have far more pressing matters on their plate than looking into opposition candidates.

Two tourist ferries on Mexico's Caribbean coast were rigged with explosives in recent weeks, and late Sunday two drug cartel executions occurred in the resort city of Cancun.

Investigations into bribes allegedly paid by Brazilian construction giant Odebrecht have also languished for years in Mexico despite high-profile prosecutions in other parts of Latin America.