Enrique Pena Nieto, the youthful candidate of the party that governed Mexico for decades, won a resounding victory in the country's presidential election, exit polls showed.
The win, when confirmed, will mark a stunning comeback for Pena Nieto's center-left Institutional Revolutionary Party (PRI), which ruled for seven decades until 2000 through a mixture of patronage and selective repression.
The daily El Universal gave Pena Nieto 42 percent of the vote, while his nearest rival, leftist Andres Manuel Lopez Obrador from the Party of the Democratic Revolution (PRD), took 31 percent.
Far behind was Josefina Vazquez Mota from unpopular outgoing President Felipe Calderon's conservative National Action Party (PAN) with 24 percent of the vote.
State-run TV Once gave almost exactly the same numbers, as did Milenio cable TV news. The first official results are expected around 0445 GMT.
Calderon's PAN has been hemorrhaging support due to the brutal drug violence that has killed over 50,000 people since he came to power in 2006.
His military crackdown on the cartels has turned parts of the country into war zones, and despite presiding over a period of steady economic growth, Calderon leaves as an unpopular president with a dubious legacy.
The economy grew under the PAN, but so did poverty: 47 percent of Mexico's 112 million residents are poor, according to government figures.
Mexico is Latin America's second biggest economy after Brazil, but there are nearly 15 million more poor people since the PRI left power, figures show. Poverty ranks second among voter concerns after insecurity.
Mexican presidents are elected by simple majority for six-year terms and are banned from running for re-election. There is no run-off vote.
Although mistrust in the electoral system runs high -- surveys suggested some 40 percent of the nearly 80 million eligible voters would not bother to show up at the polls -- some were keen to cast their vote.
"I've been here since 7:00 am to vote because it's probably the last time I can do it," said 86-year-old Maria del Pilar Amezcua, the first person to cast a ballot at her polling station in Mexico City's Huatulco neighborhood.
Election officials worked hard to convince skeptics that the ballot will be clean but faced a raft of complaints in the lead-up to the vote.
The PAN accuses the PRI of handing out more than 9,900 gift cards to influence voters. Election officials pledged an investigation but refused to freeze a bank account linked to the cards containing some $5.2 million.
The PRI has in turn accused the PRD and PAN of attempting to sway voters by handing out bags of food and building materials. And the PRD alleged "very serious irregularities" including PRI fuel charge cards.
Top election official Leonardo Valdes, however, insisted that this was "the cleanest and most impartial" Mexican election ever.
"Each vote will be scrupulously counted," he said as the vote got underway.
Nearly one million Mexicans -- including election workers, volunteer citizens and party representatives -- as well as 700 international observers were at polling stations overseeing the vote.
Also up for grabs are 500 seats in the Chamber of Deputies, where members serve for three years; 128 seats in the Senate, which has six-year terms; and various mayoralties and governorships.
Security is a top concern in Mexico. Kidnappings, drug hits and gang warfare have turned some areas into virtual war zones.
Extra army patrols were deployed in especially dangerous regions like the northern border town of Nuevo Laredo, where a car bomb -- a rarity in Mexico -- detonated Friday in front of the mayor's office.