اخبار عالمية و دولية
Polls are due to open across Mexico after a campaign marred by some of the worst political violence in the country for decades.
More than 130 candidates and political workers have been killed since campaigning began in September.
The presidential front-runner is Andres Manuel Lopez Obrador, the left-wing former mayor of Mexico City who has pledged to crack down on corruption.
He could oust the two parties that have governed Mexico for nearly a century.
Many voters are keen to replace the government of incumbent President Enrique Peña Nieto. They are angry at Mexico's sluggish economy as well as widespread corruption and crime, says BBC Mexico correspondent Will Grant.
Much of the violence during the campaign has been carried out by criminal groups attempting to control local politics, our correspondent adds.
Mr Lopez Obrador - often referred to by his initials Amlo - has made tackling corruption the central plank of his campaign, promising to improve wages and pensions by stamping out rampant abuse by the state and by political and business elites.
Mr Lopez Obrador, 64, was runner-up in the last two elections. If he wins this time, he will end the dominance of the two parties that have governed Mexico for decades - the Institutional Revolutionary Party (PRI) and the National Action Party (PAN).
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He has referred to them as being part of the same "mafia of power". He is putting forward a left-wing coalition led by his party, Morena, as a chance to make a radical break with the past.
His closest rival looks to be Ricardo Anaya of PAN who heads a centre-right coalition. Mr Anaya has tried to paint Mr Lopez Obrador as a populist and a maverick who cannot be trusted to run the economy.Image copyright Reuters Image caption Andres Manuel Lopez Obrador, (L) has been the front-runner ahead of Jose Antonio Meade (C) and Ricardo Anaya
The candidate for the governing PRI party is José Antonio Meade, a former finance minister.
As well as a new president, Mexicans will be voting for 128 senators and 500 deputies in Congress as well as state and local officials. In all, 88 million people will be eligible to vote.
Mexico is the second largest economy in Latin America and a major oil exporter. However, oil prices have dropped and the Mexican currency, the peso, has fallen sharply against the dollar.
More than 40% of the population lives in poverty. High levels of corruption and violence have led some companies to pull out of the worst affected areas.
On Saturday, a journalist was shot dead in a bar in the village of Saban in the southern state of Quintana Roo, officials said. Mexico has a reputation for being one of the most dangerous countries in the world for journalists.