Voters overwhelmingly chose Andres Manuel Lopez Obrador as Mexico's next president , embracing his leftist platforms and his criticism of US President Donald Trump.

Lopez Obrador, known by his initials "AMLO," will succeed President Enrique Peña Nieto on December 1.

He's vowed to tackle Mexico's most dire challenges -- poverty, violence and corruption -- while denouncing elitism and welcoming populism to the country's highest office.

But internationally, many will be watching how AMLO's respectful but contentious attitude toward Trump will play out.

'Listen, Trump'

When it comes to AMLO's thoughts about Trump's proposed border wall , the title of his recent book says it all: "Listen, Trump! Saying Yes to a New Start for Mexico, Saying No to a Wall," the cover reads, featuring an image of AMLO lecturing and pointing his finger

Lopez Obrador at times led by more than 20 points in the pre-election polls, as Mexicans expressed massive dissatisfaction with mainstream political parties.

In a speech to his supporters, AMLO said he would forge a new relationship with the US "rooted in mutual respect and in defense of our migrant countrymen who work and live honestly in that country."

He said migration should be done by choice -- not by necessity -- saying Mexico needs to "strengthen the internal market to try to produce in the country what we consume and so that Mexicans can work and be happy where they were born, where their family is, where their customs and their cultures are."

After AMLO's victory, Trump tweeted his congratulations and said he looked forward to working with the President-elect.

"There is much to be done that will benefit both the United States and Mexico," Trump said.

Congratulations to Andres Manuel Lopez Obrador on becoming the next President of Mexico. I look very much forward to working with him. There is much to be done that will benefit both the United States and Mexico! — Donald J. Trump (@realDonaldTrump) July 2, 2018

AMLO reciprocated the kind words Monday in an interview with CNN affiliate Televisa.

"I want to thank him (Trump) for his message, for congratulating me. It was very respectful," he said. "That is what we are looking for in our relationship with the United States -- that there is mutual respect, we will never disrespect him. ... We do not fight; we will always look for an agreement."

Victory speech mentioned migrants

AMLO made a point of mentioning migrants several times in his victory speech, emphasizing his plans to improve Mexico's economy from the ground up, with an eye toward making life better for the country's poorest and most vulnerable.

"Whoever wants to emigrate," he said, "should do it out of desire and not out of necessity."

One thing AMLO didn't mention Sunday night: how he plans to handle the thousands of migrants from Central America who come through Mexico on their way to the United States. In recent years, Mexico has deported more Central Americans than the United States

Here's what Lopez Obrador actually said, according to a video posted on his campaign website: "We are going to defend the migrants from Mexico, from Central America, from the whole American continent and all the migrants of the world that out of necessity have to abandon their villages to go seek a better life in the United States; it is a human right that we are going to defend for Mexicans and for all migrants."

Slashing his salary and calling out the 'power mafia'

AMLO ran on a populist platform, saying he's sick of the grip that Mexico's elite -- or "power mafia" -- have on the country.

So he's vowed to lower the salaries of top officials and even cut his own salary in half. (The 2016-2017 presidential salary was about 2.5 million pesos, or about $124,000, before taxes.)

He's also promised to sell presidential planes and turn the presidential palace into a public park while increasing the salaries of lower-paid government workers.

Supporters of Andres Manuel Lopez Obrador celebrate at Zocalo square in Mexico City.

Voter Dario Manuel Lopez Pineda's said AMLO, the former mayor of Mexico City, has a strong track record of helping ordinary citizens.

"He was the first to give universal pension to seniors. He created 16 high schools in marginal areas," Lopez Pineda said.

"He created such seemingly insignificant things such as permanent driver licenses so that the government would not keep taking money from the people."

Ousting corruption and fighting violence

President-elect Andres Manuel Lopez Obrador celebrates his victory in front of supporters.

In Mexico City, voter Maria del Carmen Munoz said she supported AMLO during his two previous presidential campaigns.

"The third time (was) the charm," she said. "I have supported him for so long because I believe in him, because the government we have is rotten."

Lopez Obrador said the country's infamous corruption was the "result of a political regime in decay."

"We are absolutely certain that this evil is the principal cause of social inequality and of economic inequality," he said. "Because of corruption, violence has erupted in our country."

He said he will work with representatives of the United Nations, human rights groups and religious organizations to help tackle the murder rate, which soared to an all-time high under Peña Nieto's tenure.

"The country's problems are grave," AMLO told Televisa. "But I am confident and I am willing to face these challenges."