How Biden’s Immigration Fight Threatens His Biggest Foreign Policy Win

The soaring number of people crossing into the United States from Mexico has been a political vulnerability for President Biden for the past three years, chipping away at his approval rating and opening him up to political attacks.

But now, the crisis is threatening to upend America’s support for the war in Ukraine, throwing the centerpiece of Mr. Biden’s foreign policy into jeopardy.

After a meeting with Mr. Biden at the White House on Wednesday, Speaker Mike Johnson insisted that the Republican-led House would not pass legislation to send aid to Ukraine unless Democrats agreed to sweeping new restrictions at the U.S.-Mexico border.

And even if the two sides do come to some sort of agreement, many Republicans, especially in the House, would be loath to give an election-year win to Mr. Biden on an issue that has given them a powerful line of criticism toward the White House. The issue is also at the center of the candidacy of Mr. Biden’s likely opponent this fall, former President Donald J. Trump.

The stalemate shows how the debate over immigration in the United States is no longer just about the border. The issue is spilling over into other parts of Mr. Biden’s agenda, taking on outsize influence as Republicans use it to block the president’s top foreign policy priorities.

“I think the vast majority of members of Congress support aid to Ukraine,” Mr. Biden told reporters on Thursday before traveling to Raleigh, N.C. “The question is whether or not a small minority are going to hold it up, which would be a disaster.”

Mr. Biden has characterized aid to Ukraine as a matter of American leadership on the global stage. If the United States fails to send more, he warned last month, other allies may back off their own commitments.