On President Biden’s first day in office, he paused nearly all deportations. He vowed to end the harsh practices of the Trump administration, show compassion toward those wishing to come to the United States and secure the southern border.

For Mr. Biden, it was a matter of principle. He wanted to show the world that the United States was a humane nation, while also demonstrating to his fellow citizens that government could work again.

But those early promises have largely been set aside as chaos engulfs the border and imperils Mr. Biden’s re-election hopes. The number of people crossing into the United States has reached record levels, more than double than in the Trump years. The asylum system is still all but broken.

On Friday, in a dramatic turnaround from those early days, the president implored Congress to grant him the power to shut down the border so he could contain one of the largest surges of uncontrolled immigration in American history.

“If given that authority,” Mr. Biden said in a statement, “I would use it the day I sign the bill into law.”

Some of the circumstances that have created the crisis are out of Mr. Biden’s control, such as the collapse of Venezuela, a surge in migration around the world and the obstinance of Republicans who have tried to thwart his efforts to address the problems. They refused to provide resources, blocked efforts to update laws and openly defied federal officials charged with maintaining security and order along the 2,000-mile border.