Enrique Pena Nieto, the youthful candidate of the party that governed Mexico for 71 years, has claimed victory in the country's presidential election.
Pena Nieto of the Institutional Revolutionary Party (PRI) won Sunday's election with 38 per cent of the vote, according to official results.
Pena Nieto's nearest rival was leftist Andres Manuel Lopez Obrador from the Party of the Democratic Revolution (PRD), with 31 to 32 per cent.
Pena Nieto, 45, dismissed fears of the PRI's history of corruption and authoritarianism, saying "there's no return to the past." He pledged to practice "a new way of governing," within boundaries of democracy.
"I'm going to honour your trust, and I'm going to deliver for all of Mexico," he said.
"Our party has gotten a second chance, and we're going to honour it with results."
Pena Nieto entered the PRI headquarters in Mexico City to a hero's welcome soon after the results were announced.
"Presidente! Presidente!" the crowd chanted.
"The day of voting has ended. The country now demands ... the unity of all Mexicans," he said, then thanked the other candidates by name for what he said was their contribution to democracy.
Pena Nieto also thanked outgoing President Alvaro Calderon "for his democratic vocation."
Calderon phoned Pena Nieto to congratulate him and addressed the nation to express his "complete disposition to co-operate" in the transition.
Pena Nieto was also likely to benefit from a legislative majority that no Mexican government has enjoyed for 15 years.
Sunday's election was the biggest in Mexican history, selecting a new president, both houses of Congress, six state governors and the Mexico City mayor.
About 80 million voters were registered. Mexico has no second round of voting, so the top vote-getters win office even without a majority of the votes.
In the previous presidential election in 2006, Calderon beat Lopez Obrador by 0.56 percentage points, which led to a drawn-out dispute and fraud allegations.
Mexican law limits presidents to one six-year term.
Pena Nieto has his work cut out for him. Mexico ranks 14th among the world's economies and enjoys relative economic stability but it also suffers great inequality.
While 46 per cent of Mexicans, or 52 million people, live in poverty, the country is also home to telecommunications tycoon Carlos Slim, the world's wealthiest man, according to Forbes magazine.
Security is a top concern in Mexico. The country suffers from violence by its powerful drug cartels. More than 50,000 people are estimated to have been killed in organised crime violence since Calderon took office in December 2006.
Extra army patrols were deployed before Sunday's election in especially dangerous regions like the northern border town of Nuevo Laredo, where a car bomb detonated on Friday in front of the mayor's office.