Who Could Sway the Outcome of the U.S. Election? Mexico’s President

Migrants were streaming across the U.S. southern border in record numbers, international rail bridges were abruptly shut down and official ports of entry closed.

Desperate for help in December, President Biden called President Andrés Manuel López Obrador of Mexico, who told him to quickly send a delegation to the Mexican capital, according to several U.S. officials.

The White House rushed to do so. Soon after, Mexico beefed up enforcement. Illegal border crossings into the United States plummeted by January.

As immigration moves to the forefront of the U.S. presidential campaign, Mexico has emerged as a key player on an issue with the potential to sway the election, and the White House has worked hard to preserve Mr. López Obrador’s cooperation.

The administration says publicly that its diplomacy has been a success.

But behind closed doors, some senior Biden officials have come to see Mr. López Obrador as an unpredictable partner, who they say isn’t doing enough to consistently control his own southern border or police routes being used by smugglers to bring millions of migrants to the United States, according to several U.S. and Mexican officials. None of them would speak on the record about delicate diplomatic relations.

“We aren’t getting the cooperation we should be getting,” said John Feeley, former deputy chief of mission in Mexico from 2009 to 2012. Mr. Feeley said the two countries did more joint patrols and investigations to secure the border during the Obama administration.