Enrique Peña Nieto claimed victory in Mexico's presidential election and vowed to work for reconciliation and national unity while crafting a "modern and responsible" presidency.

The Institutional Revolutionary Party, or PRI, candidate said he would continue to fight organized crime, but with a new strategy that focuses on reducing violence and safeguarding the lives of Mexicans.

"Let it be clear. There will be no pact or truce with organized crime," the 45-year-old Peña Nieto said, referring to the wave of drug-related violence that has claimed the lives of more than 50,000 people since late 2006.

Peña Nieto, according to the preliminary vote tally released by the Federal Electoral Institute, or IFE, won 37.33 percent of the vote in Sunday's general elections, with 78.47 percent of the ballots counted.

Andres Manuel Lopez Obrador, candidate of the leftist Progressive Movement coalition, won 32.55 percent of the vote, while governing National Action Party, or PAN, candidate Josefina Vazquez Mota got 25.37 percent of the vote.

Longshot Gabriel Quadri, of the New Alliance Party, or PANAL, won 2.37 percent of the vote.

Figures from the Preliminary Election Results Program, or PREP, will continue to be released over the course of the day, the IFE said.

Peña Nieto thanked the millions of Mexicans who placed their trust in him and promised to take the presidency in a new direction.

Mexico will have "a modern presidency, responsible, open to criticism, and willing to listen and take everyone into account," Peña Nieto said.

Sunday's election gives the PRI, which governed Mexico from 1929 to 2000, a second chance, Peña Nieto said.

"The country wants work, cooperation and, above all and most importantly, results," Peña Nieto said.

Mexico will be getting an administration that is "efficient, honest, transparent and accountable," Peña Nieto said.

The politician and former Mexico state governor was accompanied by his wife, actress Angelica Rivera, on the stage.

"I invite everyone to leave behind our differences and tensions from the electoral contest," Peña Nieto said.

President Felipe Calderon, of the PAN, congratulated Peña Nieto on his victory and expressed his "absolute willingness" to help bring about an orderly transition.

Calderon will leave office on Dec. 1.

Peña Nieto, for his part, praised Calderon's "democratic vocation, his conduct and respect for the electoral process," as well as his willingness to make tough decisions during his administration.

"I will meet with President Calderon to prepare a transition with a capable and experienced team to ensure that it will be orderly, transparent and stable for the entire country," Peña Nieto said.

The PRI lost the 2000 and 2006 presidential elections to the PAN.

Lopez Obrador, meanwhile, refused to concede, saying that the figures released by the IFE did not match the numbers gathered by his campaign.

"The last word has not been spoken," Lopez Obrador said. "It is important to have a recount of all the figures ... We are going to wait until we have all the information."

Lopez Obrador, a former Mexico City mayor, lost the 2006 presidential election to Calderon by 0.56 percent and has never recognized the results.

Nearly 80 million people were eligible to vote in the general elections, with the presidency, 628 congressional seats and thousands of other posts up for grabs.

A total of 141,153 polling places were open across the country.

Nearly 1 million people trained by the IFE handled the voting process, which was monitored by 2 million party representatives, more than 30,000 Mexican election observers and 696 foreign election observers. 

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