GUADALAJARA, Mexico (Reuters) - Mexico's presidential front-runner Enrique Pena Nieto emerged largely unscathed in a televised debate on Sunday night after his adversaries failed to take advantage of an increase in opposition to his bid.
During a two-hour encounter largely devoid of drama, Pena Nieto was barely troubled by his leftist rival Andres Manuel Lopez Obrador, whose recent surge in the polls has added an element of uncertainty to the July 1 vote.
In the past month, Pena Nieto's opposition Institutional Revolutionary Party (PRI) has been hit by a wave of student-led opposition playing on memories of the PRI's reputation for corruption and authoritarianism during its 71-year rule.
Lopez Obrador has been the main beneficiary of the anti-PRI surge, but he made little effort to rally that support on Sunday night, preferring instead to repeat election mantras and list the members of his planned cabinet.
"Lopez Obrador should have said 'thank you' to the student protests or 'We don't want the PRI's authoritarianism,' but he lacked the political intelligence and wasted a golden opportunity," said Javier Oliva, a political scientist at the National Autonomous University of Mexico (UNAM). "I have no doubt now that Pena Nieto is going to be the next president."
The jump in support for 2006 runner-up Lopez Obrador has pushed Josefina Vazquez Mota of the ruling National Action Party (PAN) back into third place in most polls.
She offered most of the attacks during the debate, trying to brand her adversaries as two sides of the same coin, at turns describing them as corrupt, cowardly and untrustworthy. But many analysts believe she will struggle to finish better than third.
Most polls show Pena Nieto with a double-digit lead, with a survey by polling firm BGC published on Thursday giving him 42 percent support, an advantage of 14 points over both his rivals.
Just a few months ago the 58-year-old Lopez Obrador was more than 20 points adrift in most polls. But on May 31, one survey put him just four points behind the PRI candidate.
Instead of celebrating his rise in the polls as he has on the campaign trail, Lopez Obrador sat back and came under fire in the debate from Vazquez Mota who reminded voters that he had once belonged to the PRI before he quit in the late 1980s.
Despite her spirited showing on Sunday night, her bid has suffered at the hands of growing disillusionment with the PAN.
Having ousted the PRI in 2000, the party has struggled under President Felipe Calderon to cope with drug-related violence and a weak job market, allowing Mexico's old rulers to regroup.
Tens of thousands of protestors marched against the PRI in Mexico City on Sunday, holding up banners warning that a Pena Nieto win would bring back the worst elements of his party and benefit entrenched interests like dominant broadcaster Televisa.
Some also marked the 41st anniversary of a notorious student massacre in the capital, which alongside the bloody suppression of demonstrations in the city's Tlatelolco district in 1968 are among the most infamous acts of repression tied to the PRI.
Seizing on the fact Lopez Obrador recently held a rally at the site of the 1968 killings, Vazquez Mota said he owed his followers an explanation for why he joined the PRI.
"It's really terrible you brought those young people there when it seems those corpses didn't matter to you," she said in what was the final televised debate before the election.
Since the first debate on May 6, opposition to Pena Nieto and the PRI has become much more visible, with Internet-savvy student activists organizing protests in cities around Mexico.
Trouble began brewing online for the 45-year-old Pena Nieto after May 11, when students at Mexico City's private Ibero-American University heckled and booed him for his record as governor of the State of Mexico between 2005 and 2011.
Afterwards some Pena Nieto supporters questioned whether the Ibero demonstrators really had been students, which only helped to galvanize his youth critics and spur them into action.
Vazquez Mota mocked Pena Nieto for his Ibero appearance, accusing him of taking cover from the students in a toilet.
"We don't want someone who's going to hide in the university toilets to solve the country's problems," she said.
Pena Nieto responded that he had not been hiding and said he respected the fact the students had different opinions.
Vazquez Mota also accused Pena Nieto of funding a spying network to snoop on political rivals while governor of Mexico's most populous state, though she did not follow up the attack.
By and large, Pena Nieto was able to remain above the fray, repeatedly stressing the need for greater growth and more jobs.
Vazquez Mota, who is bidding to become Mexico's first woman president, directed many of her attacks against Lopez Obrador, dismissing his plan to fund higher investment by slashing pay for high-ranking officials and eliminating corruption.
"The numbers just don't add up Mr. Lopez Obrador," she said.
Voters in Mexico City offered little indication that the debate had changed their views of the candidates.
"I was going to vote for Pena Nieto before the debate and I am still going to vote for him now," said Rafael Cortes, 57, an accountant. "The PRI politicians have problems but they have the experience to improve the economy and reduce the violence."
Additional reporting by Dave Graham, Mica Rosenberg, Ioan Grillo and Gabriel Stargardter; Editing by Bill Trott and Eric Walsh