Mexico's ruling party candidate Claudia Sheinbaum has been projected to win the presidential elections, according to exit polls released Monday.
The 61-year-old former Mexico City mayor, won around 58 percent of votes, according to an estimate by the Enkoll polling firm.
The early result has her comfortably leading opposition rival Xochitl Galvez, who had 29 percent.
First official results are expected between 10 and 11 p.m. (0400 and 0500 GMT/UTC).
The voting was overshadowed after two people were killed in violence at polling centers on Sunday amid a campaign that has already seen 38 candidates murdered, including a local candidate who was fatally shot on Saturday night. The deadly incidents have raised concerns about the threat of warring drug cartels to democracy.
Voting was brought to a halt at one polling center after a person was killed in a shooting in Comeyoapan, a town in the state of Puebla, according to the state electoral authority.
Another death at a polling station in Tlanalapan, also in Puebla, was reported by the state attorney general.
Historic vote
Sunday's election will very likely see the historic election of the country's first female president as two women vie for the top job ahead of a man running a distant third.
As polls opened, Mexico City Mayor Claudia Sheinbaum of the ruling Morena Party enjoyed a nearly 17-point advantage over opposition candidate Xochitl Galvez.
Polls have opened in Mexico's elections: DW's Nicole Ris
Sheinbaum has promised to continue the populist political program of popular outgoing President Andres Manuel Lopez Obrador, who is constitutionally barred from seeking another term in office.
Galvez, a former senator and tech entrepreneur, represents a coalition of opposition parties and has promised to change tack from Lopez Obrador's "hugs, not bullets" policy toward the country's ultra-violent drug cartels.
Cartel violence on voters' minds
Both the economy — which is struggling in the increasingly polarized country — and cartel violence are foremost on voters' minds according to opinion polls.
This would seem to come as no surprise in a campaign season marred by violence.
At least 25 candidates have been murdered since campaigning began for roughly 20,000 positions across the country — from the presidency and governorships, to both houses of Congress and various local posts.
In all, more than 450,000 people have been murdered since Mexico began fighting its war on drugs in 2006.
Thousands of soldiers have been deployed at polling stations around the country for Sunday's vote.
Ruling Morena Party hopes to expand power, change constitution
Currently, the Morena Party holds 23 of Mexico's 32 governorships as well as a simple majority in Congress. The party hopes to win a two-thirds majority in both houses in order to amend the constitution, allowing it to do away with oversight agencies it claims are wasteful.
Opposition candidates say such changes would endanger Mexican democracy.
Early turnout appeared to be high throughout most of the country on Sunday. Preliminary returns are expected around 9 p.m. (0000 GMT) Sunday evening.
js/kb (AFP, AP)