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 as campaigning wraps up, putting him on track to return the party that ruled for much of the last century to power.
The final voter survey of the campaign by polling firm Buendia & Laredo for 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 poll 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.
Another poll published Wednesday by polling firm BGC for the Excelsior newspaper put Pena Nieto's support at 44 percent of voters, giving him a 16-point lead over Lopez Obrador's 28 percent.
The Excelsior/BGC poll had Vazquez Mota, bidding to become Mexico's first woman president, in third place with 25 percent.
A third poll by the Reforma newspaper showed Pena Nieto holding his lead with 41 percent support, 10 percentage points ahead of Lopez Obrador with 31 percent.
Backing for Pena Nieto in the Reforma poll fell by 1 point from a previous survey published by the newspaper on June 19, while Lopez Obrador's support rose 1 percentage point. It gave Vazquez Mota 24 percent.
Recent polls also indicate the PRI could achieve 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, the former mayor of Mexico City, lost the 2006 election to President Felipe Calderon of the PAN 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 this year, 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 given Lopez Obrador has the support of a newly emerged student movement that shook up the campaign with huge rallies.
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 working 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 Buendia & Laredo poll surveyed 2,000 eligible voters between June 22 and June 24. It had a margin of error of 2.5 percentage points, the newspaper said.
Excelsior/BGC said it surveyed 1,200 eligible voters between June 23 and June 25 and that its poll had a margin of error of 2.9 percentage points.
The Reforma poll surveyed 1,616 voters between June 21 and June 24, and had a margin of error of 2.7 percentage points.
(With reporting by Miguel and Gutierrez; Editing by Simon Gardner and Bill Trott)