Wall Street Journal opinion columnist Mary Anastasia O'Grady said Monday that newly-elected Mexican President Andres Manuel Lopez Obrador must calm global markets in order for his government to be effective. 

The left-wing Lopez Obrador, the former mayor of Mexico City, won more than half the election's votes on Sunday and will be inaugurated Dec. 1. 

O'Grady added that she believes Lopez Obrador is going to be "very careful" at first, due to Mexico's exposure in the international market. The peso fell more than 1 percent against the U.S. dollar overnight as Lopez Obrador was elected.

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She explained that if Lopez Obrador says anything to rattle the markets over the next few months, the peso's value will drop precipitously and his government could fail even before he takes office.

O'Grady said on "The Daily Briefing with Dana Perino" that she doesn't see Lopez Obrador's policies leading to dramatic improvements in the country. 

"If there is any change, I think it's going to be for the worse."

O'Grady told Perino that an area where Mexico has lacked progress is in its rule of law, and more specifically law enforcement.

Lopez Obrador has said he will root out corruption and grant amnesties to certain criminals amid an intense wave of violence in Mexico.

O'Grady said that she doesn't see the issue of drug trafficking in the country changing under Lopez Obrador's leadership, a large driver of the country's violence.

"The fundamental problem is that this country has a huge demand for drugs," she said. "Those dollars do directly into the pockets of criminals."

Although the left-wing populist has railed against Trump's highly-contested border policies, Trump tweeted his congratulations on Monday, adding that he looks "very much forward to working with him."

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