Immigration was dead simple when Joseph R. Biden Jr. was campaigning for president: It was an easy way to attack Donald J. Trump as a racist, and it helped to rally Democrats with the promise of a more humane border policy.
Nothing worked better than Mr. Trump’s “big, beautiful wall” that he was building along the southern border. Its existence was as much a metaphor for the polarization inside America as it was a largely ineffective barrier against foreigners fleeing to the United States from Central America.
“There will not be,” Mr. Biden proclaimed as he campaigned against Mr. Trump in the summer of 2020, “another foot of wall constructed.”
But a massive surge of migration in the Western Hemisphere has scrambled the dynamics of an issue that has vexed presidents for decades, and radically reshaped the political pressures on Mr. Biden and his administration. Instead of becoming the president who quickly reversed his predecessor’s policies, Mr. Biden has repeatedly tried to curtail the migration of a record number of people — and the political fallout that has created — by embracing, or at least tolerating, some of Mr. Trump’s anti-immigrant approaches.
Even, it turns out, the wall.
On Thursday, Biden administration officials formally sought to waive environmental regulations to allow construction of 20 additional miles of border wall in a part of Texas that is inundated by illegal migration. The move was a stunning reversal on a political and moral issue that had once galvanized Mr. Biden and Democrats like no other.
The funds for the wall had been approved by Congress during Mr. Trump’s tenure, and on Friday, the president said he had no power to block their use.
“The wall thing?” Mr. Biden asked reporters on Friday. “Yeah. Well, I was told that I had no choice — that I, you know, Congress passes legislation to build something, whether it’s an aircraft carrier wall or provide for a tax cut. I can’t say, ‘I don’t like it. I’m not going to do it.’”
White House officials said that they tried for years, without success, to get Congress to redirect the wall money to other border priorities. And they said Mr. Biden’s lawyers had advised that the only way to get around the Impoundment Control Act, which requires the president to spend money as Congress directs, was to file a lawsuit. The administration chose not to do so.
The money had to be spent by the end of December, the officials said.
Asked on Thursday whether he thought a border wall works, Mr. Biden — who has long said a wall would not be effective — said simply: “No.”
Still, human rights groups are furious, accusing the president of abandoning the principles on which he campaigned. They praise him for opening new, legal opportunities for some migrants, including thousands from Venezuela, but question his recent reversals on enforcement policy.
“It doesn’t help this administration politically, to continue policies that they were very clear they were against,” said Vanessa Cárdenas, the executive director of America’s Voice, an immigrant rights organization. “That muddles the message and undermines the contrast that they’re trying to make when it comes to Republicans.”
“This president came into office with a lot of moral clarity about where the lines were,” she added.
Mr. Biden had previously adopted some of his predecessor’s policies, but those have still failed to slow illegal immigration. The issue has become incendiary inside his own party, driving wedges between Mr. Biden and some of the country’s most prominent Democratic governors and mayors, whose communities are being taxed by the cost of providing for the new arrivals.
Eric Adams, the Democratic mayor of New York, has blamed the administration for a situation that he says could destroy his city. J.B. Pritzker, the Democratic governor of Illinois and an ally of Mr. Biden, wrote this week in a letter to the president that a “lack of intervention and coordination” by Mr. Biden’s government at the border “has created an untenable situation for Illinois.”
In comments to reporters at an event opposing book banning, Mr. Pritzker said that he had recently “spoken with the White House” on the matter “to make sure that they heard us.”
The moment underscores the new reality for the president as he prepares to campaign for a second term. His handling of immigration has become one of his biggest potential liabilities, with polls showing deep dissatisfaction among voters about how he deals with the new arrivals. With record numbers of migrants streaming across the border, he can no longer portray it in the simple terms he did a few years ago.
Since taking office, Mr. Biden has tried to balance his stated desire for a more humane approach with strict enforcement that aides believe is critical to ensure that migrants do not believe the border is open to anyone.
This spring, the president announced new legal options for some migrants from several countries — Venezuela, Cuba, Nicaragua and Haiti. He also has expanded protections for hundreds of thousands of migrants already in the United States, allowing more of them to work while they are in the country temporarily.
But the more welcoming policies have been balanced by tougher ones.
Earlier this year, Mr. Biden approved a new policy that had the effect of denying most immigrants the ability to seek asylum in the United States, a move that human rights groups noted was very similar to an approach that Mr. Trump hailed as a way to “close the border” to immigrants he wanted to keep out.
The president and his aides have responded to the increased number of migrants by calling for more border patrol agents. Karine Jean-Pierre, the White House press secretary, bragged on Wednesday about the surge in border enforcement that Mr. Biden has pushed for.
“Let’s not forget,” she said. “The president got 25,000 Border Patrol, additional Border Patrol law enforcement, at the border.”
In a budget request to Congress, the Biden administration has asked for an additional $4 billion for border enforcement, including 4,000 more troops, 1,500 more border patrol agents, overtime pay for federal border personnel and new technology to detect drug trafficking.
And on Thursday, the administration announced that it would resume deporting Venezuelans who arrive illegally, essentially conceding that the policy of creating legal immigration options from that country had failed to stem the tide of new arrivals like they had expected.
Ben LaBolt, the White House communications director, said Mr. Biden proposed an immigration overhaul on his first day in office that he noted has been blocked by Republican lawmakers.
“He has used every available lever — enforcement, deterrence and diplomacy — to address historic migration across the Western Hemisphere,” Mr. LaBolt said, adding that the administration is “legally compelled” to spend the wall money. “President Biden has consistently made clear that this is not the most effective approach to securing our border.”
Despite early reports that the number of migrants had dropped this summer, crossings have soared again this fall. Border Patrol agents arrested about 200,000 migrants in September, the highest number this year, according to an administration official who spoke anonymously to confirm the preliminary data.
Still, the administration’s announcement about new construction of a wall was a surprise to many of the president’s allies, who had repeatedly heard Mr. Biden join them in condemning Mr. Trump for trying to seal the country off from immigrants.
In a notice published in the Federal Register on Thursday, Alejandro N. Mayorkas, the homeland security secretary, said that easing environmental and other laws was necessary to expedite construction of sections of a border wall in South Texas, where thousands of migrants have been crossing the Rio Grande daily to reach U.S. soil.
“There is presently an acute and immediate need to construct physical barriers and roads in the vicinity of the border of the United States in order to prevent unlawful entries into the United States,” Mr. Mayorkas said.
There have always been barriers at the border, and Democrats have voted for funding to construct them. But before Mr. Trump arrived on the scene, they were placed in high-traffic locations and were often short fences or barriers designed to prevent cars from crossing.
Mr. Trump changed that. He pushed for construction of a wall across the entire 2,000-mile border with Mexico, eventually building or reinforcing barriers along roughly 450 miles. And he insisted on a 30-foot tall wall made of steel bollards, painted black to be more intimidating. At various points, Mr. Trump said he wanted to install sharp, pointed spikes at the top of the wall to skewer migrants who tried to climb over it.
That image — of an ominous and even dangerous barrier designed to send a message of “keep out” to anyone who approached — underscored the yearslong opposition from Democrats, including Mr. Biden, to its construction. At the end of 2018, the federal government shut down for 35 days — the longest in its history — over Democratic refusal to meet Mr. Trump’s demands for $5.7 billion to build the wall.
But for Mr. Biden, the politics of immigration have changed significantly since then.
Gov. Kathy Hochul of New York put it bluntly in a letter to the president at the end of August, as New York City struggled to deal with tens of thousands of new migrants.
“The challenges we face demand a much more vigorous federal response,” she wrote. “It is the federal government’s direct responsibility to manage and control the nation’s borders. Without any capacity or responsibility to address the cause of the migrant influx, New Yorkers cannot then shoulder these costs.”
