? Enrique Pena Nieto has won Mexico' s presidential elections, preliminary results showed Sunday.

? Outgoing President Felipe Calderon congratulated Nieto on being elected next president of Mexico.

? Nieto's victory would mean a return to power for the PRI.

Mexican presidential candidate for Mexico's Institutional Revolutionary Party (PRI), Enrique Pe Nieto, shows his marked thumbs after casting his vote in Atlacomulco, State of Mexico, Mexico, on July 1, 2012. Mexican voters started casting their ballots Sunday morning to choose the country's next president, 500 deputies and 128 senators in the presidential and congressional elections. (Xinhua/David de la Paz)

The Institutional Revolutionary Party' s (PRI) candidate Enrique Pena Nieto has wonMexico' s presidential elections, preliminary results showed Sunday.

According to the quick count results of polling stations released byMexico' s Federal Electoral Institute, Nieto has won 37.93 to 38.55 percent of vote, compared to his nearest rival Andres Manuel Lopez Obrador, candidate of the Democratic Revolution Party (PRD), with around 31 percent in second place.

Josefina Vazquez Mota, presidential candidate of the ruling National Action Party (PAN), got 25 percent in the third place. A fourth candidate, Gabriel Quadri dela Torreof the New Alliance Party (Panal), got more than 2 percent of the vote.

Although the final results are planned to be announced after July 4, thepreliminary results always show high reliability inMexico's history.

Mexican outgoing President Felipe Calderon congratulated Nieto on beingelected the next president ofMexicoand promised that the current government would strengthen cooperations with Nieto's team "to guarantee the handover of power be done in an effective, well-organized and transparent manner."

"I hope that the next government can go well and continue to cater for all the Mexicans," said Calderon.

Caldron called on all classes to support the next government, promising that he would continue to work for the Mexicans until the last minute of his six-year term to provide Nieto's administration a good start.

Nieto's victory would mean a return to power for the PRI, which ruledMexicofor seven decades until its defeat in 2000 by the National Action Party's (PAN) Vicente Fox.

After the announcement of preliminary results, Nieto said that he wouldfulfill his commitments he has announced in his presidential campaign including deepening the reform, promoting economic growth and employment, eradicating poverty and inequality, adopting new strategies to fight against drug and crimes and improving social security.

However, Obrador told his supporters that he would not concede presidency until a full count.

The Federal Electoral Institute (known by its Spanish acronym IFE) said after the polls closed that about 62 percent of Mexico's 80 million eligible voters participated in the elections to choose a president, six state governors, the mayor of the capital Mexico City, 500 deputies and 128 senators.