By David Alire Garcia
MEXICO CITY (Reuters) - Mexican presidential front-runner Enrique Pena Nieto goes into Sunday's election with a wide lead over his rivals, opinion polls showed on Wednesday, putting him on track to return to power the party that ruled for much of the last century.
The final voter survey of the campaign by newspaper El Universal showed Pena Nieto, of the opposition Institutional Revolutionary Party, or PRI, rising 4.2 percentage points to 41.2 percent from a poll published on June 18.
That gave him a 17.4-point lead over leftist and 2006 runner-up Andres Manuel Lopez Obrador, who rose 0.3 percentage points to 23.8 percent, the survey showed.
Josefina Vazquez Mota, candidate of the ruling National Action Party (PAN), trailed in third place with 20.6 percent, a drop of a 0.8 percentage point from the previous survey.
Two other polls published on Wednesday, which marks the final day of campaigning, gave the PRI candidate a lead of between 10 to 16 points over Lopez Obrador, the former mayor of Mexico City.
Pena Nieto's PRI ruled Mexico between 1929 and 2000, when it was ousted by the PAN in a presidential election.
The PRI laid the foundations for modern Mexico, though the latter part of its long rule in particular was tainted by corruption, vote-rigging and heavy-handed repression of dissent.
The PAN's victory was hailed as a triumph of democracy, but its record on the economy and its failure to contain violent crime opened the door to a return by the PRI.
President Felipe Calderon has struggled to improve weak growth, unable to push through many of his planned reforms because of opposition from the PRI and other parties in Congress, where the PAN has never had a majority.
Meanwhile rampant violence between drug cartels and their clashes with the state has claimed more than 55,000 lives since 2007, further eroding confidence in the government.
Calderon sent in the armed forces to bring the gangs to heel soon after taking office in December 2006, but despite capturing or killing many top bosses, the bloodshed has escalated.
Another poll published for the Excelsior newspaper put Pena Nieto's support at 44 percent, a 16-point lead over Lopez Obrador. That poll had Vazquez Mota, who is bidding to become Mexico's first woman president, in third place with 25 percent.
A third poll by the Reforma newspaper showed Pena Nieto maintaining a sizeable lead with 41 percent support, 10 percentage points ahead of Lopez Obrador on 31 percent.
Recent polls suggest the PRI could win a working majority in both the Senate and lower house of Congress.
That would help strengthen its mandate to push through fiscal and energy reforms that stalled under Calderon.
Lopez Obrador lost the 2006 election to Calderon in a tight finish and contested the results, staging months of protests and unnerving investors in Latin America's second-largest economy.
He has stirred up fears of a repeat of the chaos, accusing the PRI of trying to rig the vote, although any protests likely would be short-lived if Pena Nieto wins by a wide margin.
A close result would raise the risk of demonstrations, particularly as Lopez Obrador has the support of a newly emerged student movement that shook up the campaign with huge rallies.
BREAK FROM PRI'S PAST
Mexican financial markets already have factored in a Pena Nieto win, so a close finish that puts his mandate and economic reforms at risk could spook investors and hit asset prices.
Pena Nieto has pledged a tax overhaul and to open up state oil monopoly Pemex to more private investment, breaking with the traditions of the PRI, which nationalized Mexico's oil industry in 1938.
The bold steps he has promised to boost outside involvement in oil exploration, refining and production are central to his bid to revamp the PRI's image and plans to boost the economy.
But even if he wins the election and his party secures a majority in Congress, Pena Nieto faces a challenge to shake up Pemex, which is struggling with a heavy tax burden, bloated workforce and oil fields in decline.
The three polls were conducted between June 21 and 25 using samples of 1,200-2,000 eligible voters. The margin of error for the polls was 2.9 percentage points or lower.
(With reporting by Miguel and Gutierrez; Editing by Simon Gardner and Anthony Boadle)