Former President Vicente Fox is asking Mexicans to unite behind the Institutional Revolutionary Party's candidate if he wins the presidency, a stunning call given that Fox ended that party's 71-year grip on power in historic 2000 elections.

Fox's comments over the weekend angered members of his own governing National Action Party, whose candidate is badly trailing Enrique Pena Nieto of the PRI, as the former ruling party is known, in the polls.

"It is clear there is an apparent winner" in the July 1 election, Fox said, referring to Pena Nieto's lead in the polls. He added that "we should unite around the winner."

When Fox defeated the PRI as the National Action candidate, his victory was seen as heralding the arrival of true democracy to Mexico. The PRI had governed Mexico since 1929 with what critics said was a blend of authoritarianism, corruption and electoral fraud.

That's why members of his own party were enraged when Fox called it unfounded fear that a PRI win in July would mark a return to Mexico's authoritarian past.

"We shouldn't be afraid that authoritarianism will return, that is a farce," Fox said. "Today we have an authentic balance of powers ... today we have democratic structures."

National Action party leader Gustavo Madero said Fox was expressing "an attitude that kept Mexico sunken in authoritarianism for seven decades."

National Action's presidential candidate, Josefina Vazquez Mota, called Fox's comments "completely senseless."

"He says that it doesn't matter if authoritarian rulers return, because now we have a democracy," she said.

"With all due respect, Vicente Fox is wrong," Vazquez Mota said. "That authoritarian Mexico can never return to the nation's life."

Fox's comments even outraged leftist presidential candidate Andres Manuel Lopez Obrador, who has recently overtaken Vazquez Mota in the polls.

"That's low," he said. "I can't believe he is wavering in support for his own party's candidate, and now, out of opportunism, he is supporting Pena Nieto."

Fox has distanced himself from the conservative National Action's current leadership.

Previously, he has suggested that the PRI was likely to win, and that the government should strike a deal with drug traffickers to ease the country's violence.

The latter call was particularly irritating to Fox's successor and current president, Felipe Calderon, who has made battling the drug cartels the centerpiece of his National Action administration.

Fox has been one of the most outspoken and unpredictable of Mexico's ex-presidents. For decades, former leaders in Mexico were expected to exit the political stage and keep largely quiet once their terms ended.