At the same time that Mr. Trump has tried to build support for his insistence on the wall, he has torn open a deep rift with fellow Republicans over his pullout from Syria and drawdown in Afghanistan, which many in the party and in cable news control rooms have deemed a more consequential break.
And, unlike in earlier shutdowns, when lawmakers have worked through the night to try to bridge policy differences, Democrats on Capitol Hill see little reason to compromise, given that the president went back on his word to avert the shutdown and that they will gain even more negotiating leverage come Jan. 3, when they take control of the House.
Mr. Trump has made a somewhat bigger effort to fan the flames, though with mixed results. He canceled a holiday vacation to his Florida estate, Mar-a-Lago, and on Saturday convened a handful of the archconservative lawmakers who had pushed him into the shutdown for a private lunch in the White House residence.
“He is not going to yield,” Mr. Meadows, who attended the lunch, said in an interview. “At some point he in some way is going to get money to support our border. He is resolved in that, and I looked him in the eyes yesterday, and I can tell you that he is firm.”
But by Sunday, increasingly isolated inside the White House with no public schedule, Mr. Trump had outwardly moved on to other issues. On Twitter, he announced the expedited departure of Defense Secretary Jim Mattis, said he had spoken with the Turkish president about Syria, expressed condolences to tsunami victims in Indonesia, said the news media had not given him his due for criminal justice and farm legislation, and mocked Mr. Corker.
Mr. Trump, who calls himself a master dealmaker, has made no effort to directly negotiate with Senator Chuck Schumer of New York, the top Senate Democrat, who would have to agree to any wall funding. Instead, he has left the job to aides, dispatching one of them, Mick Mulvaney, the budget director and incoming chief of staff, to appear on television on Sunday morning to tamp down expectations that a deal could be coming anytime soon.
“It’s very possible the shutdown will go beyond the 28th and into the new Congress,” Mr. Mulvaney said on ABC’s “This Week.”