The first official results have been released in Mexico's elections, and Enrique Pena Nieto of the opposition Institutional Revolutionary Party (PRI) is set to become the next president.
With more than 97 per cent of the votes counted from Sunday's elections, the country's federal election institute on Monday put Pena Nieto in the lead, winning 38 per cent of the vote.
Pena Nieto, of the Institutional Revolutionary Party (PRI), won Sunday's election with about 38 percent of the vote, 6.4 percentage points ahead of leftist Andres Manuel Lopez Obrador, who has yet to concede and threatened to challenge the outcome .who has yet to concede and threatened to challenge the outcome.
Leftist candidate Andres Manuel Lopez Obrador from the Party of the Democratic Revolution (PRD) gained 30 per cent of the vote and ruling party candidate Josefina Vasquez Mota conceded defeat after trailing with 25 per cent.
Many polls predicted that Pena Nieto, 45, would win by at least a 10 percentage point.
"We're a new generation. There is no return to the past," Pena Nieto said in his victory speech.
"It's time to move on from the country we are to the Mexico we deserve and that we can be ... where every Mexican writes his own success story."
Barack Obama, the US president, phoned Pena Nieto to congratulate him on his victory, promising his commitment to working in partnership with Mexico.
Al Jazeera's Adam Raney, reporting from Ciudad Juárez , said the people he had spoken to "have high hopes for big change".
"But I do not know how much they see this as a new dawn," he added.
"He [Pena Nieto] realises that he has to have results - and have them fast ... everyone is looking to him to improve two things: security in the country and the economy.
"You have about 58 million Mexicans earning less than $150 a month ... People have a lot of concerns and they want to see if he's going to hold on to his promises."
Some voters said they were waiting to see if the PRI would bring about real change.
"Let's give PRI a chance [and] ... see if they have changed or not. What happened is in the past. But what I don't want is anything that has to do with the outgoing PAN," said street musician Jose Luis Duran.
Socorro Olavez, a driver, said: "Let's hope we're done with corruption. That it stops. And they let us get to work."
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Pena Nieto's main challenger, Lopez Obrador, refused to concede defeat, saying he would await a full count and legal review.
At a news conference in Mexico City later on Monday, Lopez Obrador, 58, labeled the election as "plagued with irregularities," accused the PRI of buying votes, and said his camp would formally contest the results if they were confirmed.
In 2006, Lopez Obrador paralysed Mexico City streets with hundreds of thousands of supporters when he narrowly lost to President Felipe Calderon.
This time, only about 700 gathered at his campaign rally and he cancelled plans to proceed to the Zocalo, the main square he filled as recently as Wednesday.
"We have information that indicates something different from what they're saying officially," he said. "We're not going to act in an irresponsible manner."
Our correspondent said Lopez Obrador, who had promised to respect the results, had taken a "more measured stance than he did last time".
When he lost in 2006, Lopez Obrador went ahead and took oath as the "legitimate" president and even appointed a cabinet.
Pena Nieto's PRI governed Mexico for 71 years until losing in 2000. He has pledged to open state-owned oil monopoly Pemex to foreign investors, raise tax revenue and liberalise the labour market.
'Time to return'
Ruling party candidate Vazquez Mota's campaign was hampered by a brutal war with drug cartels and the government's patchy economic record.
"It's time for the PRI to return. They're the only ones who know how to govern," said Candelaria Puc, 70, as she voted in the beach resort of Cancun.
"The PRI is tough, but they won't let the drug violence get out of control."
Others feared a return to the worst years of PRI rule and put Pena Nieto's big lead down to his cozy 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.
The party 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.