For much of the Biden administration’s first three years in office, migration surged at the Mexican border. Administration officials frequently argued that the problem was beyond their control — a reflection not of U.S. policy but of global forces pushing people toward the border.

Then, starting in December, when the issue threatened President Biden’s re-election, he began a crackdown. The traffic of people crossing the border plummeted. Today, it remains near the lowest point since 2020 and not so different from levels during parts of the Trump and Obama administrations. This week, the Biden administration imposed tough new rules to keep it that way.

In today’s newsletter, I’ll explain how the policy has had such a big effect and why it took so long for the administration to enact.

The crisis deepens

Border crossings reached record levels this past winter, with almost 250,000 migrant arrests in December alone. At one point, U.S. officials shut down rail crossings and one port of entry, frightening businesses that ship goods between the countries. Just 32 percent of Americans thought Biden was handling immigration wisely.

Two efforts this year by the Biden administration made a big difference.

First, it pushed Mexico to clamp down on the number of migrants headed to the southern border. Mexico had run out of money to deport those people to their home countries. Then the secretaries of state and homeland security visited in late December to ask for more enforcement. Soon, the authorities there found the money to bus migrants far away, to southern Mexico. Arrests at the U.S. border dropped by half in January and stayed steady for several months.