Sixty-four-year-old leftist Andres Manuel Lopez Obrador, who got his start in Mexican politics decades ago as an advocate for indigenous rights, has won the country's presidential election.

Lopez Obrador called Sunday for "better relations" with the United States.

"We will search for a relationship with the U.S. government based on friendship and development, always inculcated with mutual respect and in defense of our compatriots, immigrants who live and work in that country," he said.

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Addressing the domestic challenges of Mexico, Lopez Obrador said eradicating corruption and impunity will be the primary mission of his government and he will “not fail” the Mexican people.

"I reiterate my promise to not betray your confidence which millions of Mexicans have placed in me. I will govern honestly and justly, I will not fail you. I will not disappoint you and I will not betray my people," he said.

U.S. President Donald Trump, congratulated Lopez Obrador Sunday on Twitter: "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!"

An exit poll by Parmetira had Lopez Obrador winning with between 53 to 59 percent of the vote, far ahead of his two main rivals.

Polls conducted before Sunday's vote consistently showed Lopez Obrador, widely known as AMLO, with a double-digit lead.

Both of Lopez Obrador's opponents in Sunday's vote — Jose Antonio Meade, of the ruling PRI party, and the PAN Party's Ricardo Anaya — wished him success "for the well-being of Mexico."

This is the first presidential election for Lopez Obrador's party, the National Regeneration Movement (MORENA), which has formed a coalition with the left-wing Labor Party and right-wing Social Encounter Party.