Polls close in Mexican presidential elections

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

The principal focus is on which of four candidates will be elected to the presidency: Andres Manuel Lopez Obrador, Ricardo Anaya, Jose Antonio Meade or Jaime Rodriguez Calderon. According to the Mexican Election Institute, more than 18,000 other posts are up for grabs, too, including congressional seats, governorships and municipal positions.

Whoever wins will have to contend with US President Donald 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.

But 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.

Leftist frontrunner Andres Manuel Lopez Obrador, who at times led polls by as much as 20 points, ran on a platform to break what he described as the grip that elites -- or "power mafia" --- have on Mexican society.

Known by his initials, AMLO 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, is 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.

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.

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.

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

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.

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.