By Mica Rosenberg and David Alire Garcia
MEXICO CITY (Reuters) - The party that ruled Mexico for much of the 20th century claimed victory in a presidential election on Sunday as exit polls showed its candidate, Enrique Pena Nieto, with a clear lead and primed to restore it to power after 12 years in opposition.
Pena Nieto, 45, of the Institutional Revolutionary Party (PRI), led by between 5 and 11 percentage points in exit polls published by three of Mexico's main television networks.
Shortly afterward his campaign manager, Luis Videgaray, declared victory.
"It is a resounding triumph," Videgaray told Milenio television, adding that he was hopeful the PRI would have a majority in the Senate and possibly in the lower house of Congress, too.
The PRI, which governed Mexico for 71 years until losing power in 2000, has staged a comeback behind the telegenic Pena Nieto, who is promising to open state-owned oil monopoly Pemex to foreign investors, raise tax revenue and liberalize the labour market.
The exit polls showed Pena Nieto winning around 40 percent of the vote, with his leftist rival Andres Manuel Lopez Obrador in second place. But it appeared to be a closer finish than predicted in final opinion polls that last week showed Pena Nieto ahead by between 10 and 15 points.
Josefina Vazquez Mota, the conservative candidate of the ruling National Action Party, or PAN, trailed in third place and said the voting trends did not favour her, virtually conceding the race.
"The new government ... will have the great responsibility to fulfil its promises and commitments. My party will act responsibly and watch out to make sure that they follow through and make it happen," she told supporters.
Vazquez Mota's campaign was hurt by outgoing President Felipe Calderon's failure to bring under control a brutal drug war and oversee strong economic growth.
"We're lacking a president who can really change the country, who can put an end to all the kidnappings, and all the lawlessness," said Daniela Flores, a 35-year-old Pena Nieto supporter who was selling party pins outside the PRI's headquarters in Mexico City.
Early official results also showed Pena Nieto with a lead, but Lopez Obrador made no public appearance on Sunday night and he could choose to challenge the election.
When he narrowly lost the last election in 2006, he launched months of protests against alleged fraud, and has said in recent weeks that this election campaign was dogged with irregularities, raising concerns that he might again call his supporters onto the streets.
A crowd of some 500 demonstrators gathered in Mexico City on Sunday night, shouting "Out with Pena" and chanting slogans in favour of Lopez Obrador, who was meeting with close advisers.
Still, Mexico's peso currency firmed 0.72 percent to 13.2601 per dollar, its strongest level in nearly eight weeks. Pena Nieto has promised pro-market policies while Lopez Obrador has scared investors with his radical rhetoric.
The country's benchmark 10-year bond closed on Friday at a record low of 5.33 percent.
Some voters feared a return to the worst years of PRI rule and put Pena Nieto's big lead down to his cosy relationship with Televisa, Mexico's top broadcaster.
"It's the same party as ever and the people who vote for him (Pena Nieto) believe they are going to live happily ever after like in the soap operas," Humberto Parra, a systems engineer, said as he went to vote in Mexico City.
By the time it lost to the PAN in 2000, the PRI had a reputation for widespread corruption, electoral fraud and authoritarianism.
The PRI was in disarray by 2006, when its presidential candidate came in a distant third, but it has rebounded since then and Pena Nieto gave it a new face.
He is promising to restore security to cities and towns ravaged by the drug war and he also plans to reform Pemex, a proposal once considered political suicide.
Mexicans are fiercely protective of Pemex, but the PRI, which nationalized oil production in 1938, could be the one party able to liberalize the energy industry.
The PRI laid the foundations of the modern state with a nimble blend of politics and patronage that allowed it to appeal to labour unions and captains of industry at the same time.
Mexicans eventually tired of heavy-handedness that stifled dissent, rewarded loyalists and allowed widespread corruption.
(Additional reporting by Miguel Angel Gutierrez, Ana Isabel Martinez, Pablo Garibian and Ioan Grillo; Writing by Daniel Trotta; Editing by Dave Graham, Kieran Murray and Christopher Wilson)
