Mexican voters are going to the polls today for presidential, national and local elections, with a populist left-wing candidate expected to become the country's next president.

The election campaign has been marred by political violence amid the country's ongoing drug war - with BBC reporting that more than 130 candidates and political workers have been killed since September.

64-year-old Andrés Manuel López Obrador - often referred to as AMLO - has a clear lead in the four-candidate presidential race, with some polling showing him more than 20 points ahead of his nearest rival Ricardo Anaya.

The favourite has soared to the top of the polls after two previously unsuccessful attempts, and comes amid widespread dissatisfaction with the current administration led by Enrique Peña Nieto.

He is promising to end the country's high murder rate, and also pledging to tackle poverty and corruption in the country.

If elected, AMLO would be the first left-wing politician to take the presidency in several decades and mark a major rejection of the political establishment.

Presidential candidate Andres Manuel Lopez Obrador, of the MORENA party, holds his closing campaign rally at Azteca stadium in Mexico City, Wednesday. Picture by: Ramon Espinosa/AP/Press Association Images

At a campaign event earlier this week quoted by Reuters, López Obrador told tens of thousands of supporters: “The country will be cleansed.

“It’s going to be a peaceful, orderly but deep transformation." 

Polls open at 8am local time, with voters also set to choose 128 senators, 500 members of the lower house and hundreds of local representatives.