PHOTO: Getty Images
Now playing
02:22
Violences looms over Mexico presidential election
Mugshots of "Juan Carlos N" and "Patricia N" who are accused of killing at least 10 women.
PHOTO: Mexico Attorney General
Mugshots of "Juan Carlos N" and "Patricia N" who are accused of killing at least 10 women.
Now playing
01:45
Couple arrested with body parts in stroller
View of the Plaza Garibaldi square in downtown Mexico City on September 15, 2018 a day after gunmen dressed as mariachi musicians killed four people and wounded nine others. - The five assailants carried out the shootings shortly before 10pm on Friday (0300 GMT Saturday) in the busy Plaza Garibaldi -popular with foreign tourists. Neither the motive for the attack nor the identities of the gunmen were known, but the area is located near the Tepito neighbourhood, where a cartel considered the largest criminal organization in the capital operates. (Photo by Alfredo ESTRELLA / AFP)        (Photo credit should read ALFREDO ESTRELLA/AFP/Getty Images)
PHOTO: ALFREDO ESTRELLA/AFP/Getty Images
View of the Plaza Garibaldi square in downtown Mexico City on September 15, 2018 a day after gunmen dressed as mariachi musicians killed four people and wounded nine others. - The five assailants carried out the shootings shortly before 10pm on Friday (0300 GMT Saturday) in the busy Plaza Garibaldi -popular with foreign tourists. Neither the motive for the attack nor the identities of the gunmen were known, but the area is located near the Tepito neighbourhood, where a cartel considered the largest criminal organization in the capital operates. (Photo by Alfredo ESTRELLA / AFP) (Photo credit should read ALFREDO ESTRELLA/AFP/Getty Images)
Now playing
00:40
Men dressed as mariachi musicians kill 5
mexico playa del carmen map
PHOTO: HLN
mexico playa del carmen map
Now playing
00:47
5 killed in shooting at Mexico nightclub
pkg romo mexico missing students pronounced murdered_00000124.jpg
pkg romo mexico missing students pronounced murdered_00000124.jpg
Now playing
02:20
Mexico officially declares missing students murdered
mexico prison riot darlington lklv_00023713.jpg
PHOTO: AFP/Getty Images
mexico prison riot darlington lklv_00023713.jpg
Now playing
02:57
Dozens dead in suspected prison riot in Mexico
new video el chapo booking pkg romo _00000505.jpg
new video el chapo booking pkg romo _00000505.jpg
Now playing
02:10
Video shows 'El Chapo' being booked
mexican missing students one year anniversary romo pkg_00010614.jpg
mexican missing students one year anniversary romo pkg_00010614.jpg
Now playing
01:55
Missing Mexican students' parents still seek answers
pope francis tuesday mass lklv flores_00002609.jpg
pope francis tuesday mass lklv flores_00002609.jpg
Now playing
01:14
Pope Francis speaks at the epicenter of Mexico's drug war
mexico el chapo birthplace romo pkg_00015819.jpg
mexico el chapo birthplace romo pkg_00015819.jpg
Now playing
02:13
Code of silence reigns in 'El Chapo' birthplace
mexico missing students contradiction romo pkg_00000727.jpg
mexico missing students contradiction romo pkg_00000727.jpg
Now playing
02:04
Report: No evidence missing Mexican students burned
romo missing student id_00000113.jpg
romo missing student id_00000113.jpg
Now playing
01:52
Remains of Mexican student identified
mexico ali landry relatives dead romo_00012916.jpg
PHOTO: From alejandromonteverde77
mexico ali landry relatives dead romo_00012916.jpg
Now playing
01:54
Ali Landry's father-in-law, brother-in-law found dead
In Eagle Pass, Texas, where poverty and dirt roads outnumber jobs and opportunities, Mexico's drug cartels prey on kids --- offering them thousands of dollars to smuggle hundreds of pounds of drugs each week.
PHOTO: Evelio Contreras/CNN
In Eagle Pass, Texas, where poverty and dirt roads outnumber jobs and opportunities, Mexico's drug cartels prey on kids --- offering them thousands of dollars to smuggle hundreds of pounds of drugs each week.
Now playing
03:59
No way out: Drug cartels recruit kids for life
(CNN) —  

Mexican voters headed to the polls Sunday to choose their next president and thousands more elected officials in a historic and consequential election marred by violence.

Voting ended in Mexico City at 9 p.m. ET. Preliminary results were expected to start coming in three hours later.

Within an hour of polls closing, three of the four presidential candidates conceded defeat to leftist frontrunner Andres Manuel Lopez Obrador, who has pledged to crack down on corruption and violence and to stand up to US President Donald Trump.

Mexico's presidential candidates, from left: Ricardo Anaya, Andres Manuel Lopez Obrador, Jose Antonio Meade and Jaime Rodriguez Calderon.
PHOTO: ine
Mexico's presidential candidates, from left: Ricardo Anaya, Andres Manuel Lopez Obrador, Jose Antonio Meade and Jaime Rodriguez Calderon.

For many of the 89 million eligible Mexican voters, Sunday’s election was a referendum on the country’s political elite and its economic direction, as well as the tenure of current President Enrique Peña Nieto, who is limited to a single six-year term.

Mexican millennials and the so-called Generation Z, many of whom have grown up surrounded by rampant corruption and drug violence, were expected to play a key role in choosing the country’s direction on Sunday. Nearly 13 million voters between the ages of 18 and 23 were expected to vote for the first time, according to election officials.

The four candidates

Homicide rates soared to an all-time high under Peña Nieto, whom critics accused of failing to adequately deal with crime, corruption and economic inequality. Some of his would-be successors campaigned on promises to correct course.

The new president will have to contend with President Trump’s threats to pull out of the North American Free Trade Agreement and his calls for the construction of a border wall between the two countries, among other divisive talking points. Lopez Obrador, who at times led polls by as much as 20 points, told voters that he is the person for the job.

Andres Manuel Lopez Obrador arrives to cast his vote during the Mexican election on July 1, 2018 in Mexico City, Mexico.
PHOTO: Pedro Mera/Getty Images
Andres Manuel Lopez Obrador arrives to cast his vote during the Mexican election on July 1, 2018 in Mexico City, Mexico.

Known by his initials, AMLO, he pushed back against plans for a wall in a book he wrote titled “Oye Trump, or “Listen Trump.” He also pledged to propose to keep NAFTA.

He ran on a populist platform to break what he described as the grip that elites – or “power mafia” — have on Mexican society. He said he would lower the salaries of top officials and give those at the bottom a pay raise. He promised to sell the presidential planes and turn the presidential palace into a public park.

The former mayor of Mexico City began his political career as a member of the ruling Institutional Revolutionary Party (PRI). He later joined the Party of the Democratic Revolution and more recently formed his own party, the National Regeneration Movement – known as MORENA. Despite his long political resume, many observers considered the 64-year-old candidate an outsider.

His critics say he has an authoritarian streak and could be Mexico’s Hugo Chavez, referring to the Venezuelan president who led his country to socialism and economic ruin. This race marks Lopez Obrador’s third presidential bid. After he lost the presidential election in 2006, he called the results a fraud and spent weeks camping out in protest with thousands of supporters in Mexico City. When he lost again in 2012, he claimed fraud kept him from winning the presidency.

Ricardo Anaya Cortés, 39, was the candidate and former national leader of the conservative National Action Party (PAN), which governed Mexico for 12 years before Peña Nieto took office in 2012. He leads a coalition of parties and is considered the most viable candidate to derail Lopez Obrador’s taking power.

Ricardo Anaya and his family give their inked thumbs up after he cast his vote during in Queretaro.
PHOTO: PEDRO PARDO/AFP/Getty Images
Ricardo Anaya and his family give their inked thumbs up after he cast his vote during in Queretaro.

He’s held multiple seats in public office in the state of Querétaro and served in the lower chamber of Congress. A technocrat and lawyer by training, he soared through the ranks using his intellect and ability to sideline rivals. Critics have accused him of involvement in potentially illegal real estate dealings, accusations which he denies.

Jose Antonio Meade, 49, is Mexico’s former finance minister. The Yale-educated lawyer and economist is the candidate for the ruling Institutional Revolutionary Party, or PRI, which had been in power for 70 years until the election of Vicente Fox of the National Action Party in 2000.

Jose Antonio Meade of the  "Todos por Mexico" coalition party casts his vote during general elections in Mexico City.
PHOTO: JOHAN ORDONEZ/AFP/Getty Images
Jose Antonio Meade of the "Todos por Mexico" coalition party casts his vote during general elections in Mexico City.

Meade has held several cabinet posts across two administrations, including secretary of foreign affairs and secretary of social development for Peña Nieto. Although Meade has a reputation for personal honesty, his party has been dogged by corruption allegations, including a scandal involving the purchase of a mansion by Peña Nieto’s family.

Jaime Rodríguez Calderón, 60, was considered the long-shot candidate in the race, running as an independent. The former governor of the industrial state of Nuevo Leon is known as “El Bronco,” or wild horse, for his strong personality and outlandish statements. During a presidential debate. he called for chopping off thieves hands to counter Mexico’s surging crime wave.

Jaime "El Bronco" Rodriguez Calderon casts his vote in Monterrey, Mexico.
PHOTO: GABRIELA PEREZ/AFP/Getty Images
Jaime "El Bronco" Rodriguez Calderon casts his vote in Monterrey, Mexico.

The winner of Sunday’s presidential election doesn’t need an absolute majority of the votes, just the most votes among the four candidates. The new president will take office on December 1.

Many politicians have been killed during the campaign

According to the Mexican Election Institute, more than 18,000 other posts are up for grabs, too, including congressional seats, governorships and municipal positions.

This campaign season in Mexico was especially violent. In the nine months leading up to this weekend’s presidential election, at least 132 politicians have been killed, according to the security consulting group Etellekt.

Of those, 48 were candidates running for office.

PHOTO: Etellekt

One of the most shocking deaths occurred last month, when congressional candidate Fernando Puron was shot in the head while posing for a photo in the northern state of Coahuila. Puron was just one of 12 Institutional Revolutionary Party members to lose his life, per Etellekt.

CNN’s Ray Sanchez, Marilia Brocchetto and Flora Charner contributed to this report.