By Gabriela Lopez
MONTERREY, Mexico, June 27 (Reuters) - Mexico's presidential front-runner Enrique Pena Nieto scented victory as he wrapped up his campaign on Wednesday with polls showing he should easily win Sunday's election and put the country's old rulers back in power.
Voters elect a new president on Sunday and many are eager for the next government to end rampant violence by drug gangs and fire up an underperforming economy, sore points that have eroded confidence in the ruling National Action Party, or PAN.
Pena Nieto is running for the opposition Institutional Revolutionary Party (PRI), and he told voters in the northern industrial city of Monterrey the party's return to power would mark a turning point in the fight against organized crime.
"We will reduce poverty and regain peace and security in the whole country," Pena Nieto, 45, told thousands in the city that was once a model for economic development in Latin America but is now mired in some of the worst violence of the drug war.
The PRI laid the foundations of modern Mexico and ruled for most of the 20th century but is widely remembered for its corruption and suppression of dissent.
The PRI was ousted by the conservative PAN in 2000 but has bounced back in the last few years, insisting it has learned from its mistakes and swinging the full might of its formidable party machinery behind the telegenic Pena Nieto.
The PAN raised high hopes when it came to power, but annual economic growth averaged barely 2 percent under its two governments and it has failed to contain spiraling criminal violence, crippling its hopes of a third term.
Three polls published on Wednesday all showed him with a double-digit lead over his rivals.
Wearing red baseball caps and red and white T-shirts handed out by the party, supporters shouted "Presidente, Presidente" as Pena Nieto took the stage in Toluca. But the rally was otherwise largely subdued.
"We have to give the PRI another chance, the PAN has shown it was not up to the job," said Ignacia Rodriguez, 50, a street vendor in Toluca. "They've failed the test."
Pena Nieto's closest rival is leftist candidate Andres Manuel Lopez Obrador, a former mayor of Mexico City who narrowly lost the 2006 election to President Felipe Calderon and then contested the results, staging months of protests that unnerved investors in Latin America's second-largest economy.
He has recently stirred up fears of new unrest, accusing the PRI of trying to rig the vote.
"People want real change and they cannot prevent it even with dirty tricks or buying loyalty, consciences and votes," Lopez Obrador told supporters at his final campaign rally in Mexico City's packed main square, or Zocalo, adding that his campaign's own poll showed him winning.
Some protesters vowed to take to the streets again if Lopez Obrador issues a rallying call, but any protests would likely be short-lived if Pena Nieto wins by a wide margin.
The prospect of a PRI victory fills some Mexicans with fear that the country is heading back towards a state dominated by one party.
"Lopez Obrador is the only option not to return to a dictatorship," said drama student Mezli Gutierrez, 24, as she joined thousands marching to the rally. "The PRI is a completely rotten system."
PAN candidate Josefina Vazquez Mota told supporters at her final campaign rally near Mexico's second city, Guadalajara, that voters needed to be mindful of foul play on Sunday.
"I invite you all to be election observers, so no-one's vote is manipulated and no-one feels pressured," she said.
Pena Nieto underlined his commitment to change in an interview published on Wednesday in the newspaper El Universal.
"There is a new PRI ... It's the others who have not changed. They are living in the past," he said. "But the PRI never left. It has lost and won, competed democratically and understood change."
Calderon's struggles with the sputtering economy have been exacerbated by the PAN's lack of a majority in Congress.
He has been unable to push through many of his planned reforms due to opposition from the PRI and other parties, and the brutality of drug war violence has eroded his standing.
Rampant violence between drug cartels and their clashes with the state has claimed more than 55,000 lives since 2007.
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 drug bosses, the bloodshed has escalated.
Pena Nieto is planning to boost growth with reforms similar to those his party helped thwart in Congress under Calderon.
He has pledged to overhaul the tax system and open up state oil monopoly Pemex to more private investment in exploration, refining and production, breaking with traditions of the PRI, which nationalized Mexico's oil industry in 1938.
Recent polls suggest the PRI could win a working majority in both the Senate and lower house of Congress.
But even if he has the majorities, Pena Nieto faces a challenge to shake up Pemex, which is struggling with a heavy tax burden, bloated workforce and oil fields in decline.
A close election 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.
In Mexico City, banners peppered the main thoroughfare, which Lopez Obrador brought to a standstill with post-election protests six years ago, reading: "I remember the devaluations, the killings, the corruption. Don't vote for the PRI."
Mexican financial markets have already 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.
The final three polls of the campaign gave the PRI candidate a lead of between 10 and 17 points over Lopez Obrador with the PAN's Josefina Vazquez Mota trailing in third.
They were conducted between June 21 and 25 using samples of 1,200 to 2,000 eligible voters. The margin of error for the polls was 2.9 percentage points or lower. (With reporting by Michael O'Boyle in Zapopan, Ioan Grillo, Miguel Angel Gutierrez, Gabriel Stargardter, Mica Rosenberg, Lizbeth Diaz and David Alire Garcia in Mexico City; Writing by Simon Gardner.; Editing by Kieran Murray and Christopher Wilson)