A last-ditch gambit to spare Senate Republicans a hostile showdown with President Trump over the Constitution’s separation of powers was torpedoed on Wednesday by the president himself, increasing the likelihood that the Senate will vote on Thursday to overturn the president’s emergency declaration and force the first veto of his term.
Hoping to avoid a confrontation with Mr. Trump over his declaration of an emergency to build his coveted border wall, Republicans tried to rally behind legislation to limit the power of presidents to declare emergencies in the future while allowing the current president’s end-run around Congress.
But Speaker Nancy Pelosi quickly derided that idea and then Mr. Trump threw cold water on it himself, phoning the Republican author of the new legislation, Senator Mike Lee of Utah, during a Senate luncheon to inform him it was no deal.
As a result, Mr. Lee said he would now vote to end the emergency declaration, the fifth Republican “yes” vote — and other Republicans, with no alternative route, are likely to follow.
“Unfortunately, it appears the bill does not have an immediate path forward, so I will be voting to terminate the latest emergency declaration,” said Mr. Lee, who had earlier said he did not think the president’s actions were unconstitutional.
The outcome left Republicans with a difficult choice. They can back the president in what is widely seen as a surrender of Congress’s core power of controlling federal spending. Or they can join Democrats and break with a president who is popular within the party on his maneuver to build a wall that is also popular with Republicans.
To Mr. Trump, the decision is not all that tough.
“I think anybody going against border security, drug trafficking, human trafficking, that is a bad vote,” the president told reporters at the White House as he delivered another warning shot to Republicans who would dare to buck him. He also defended the constitutionality of his declaration despite the bipartisan refusal of Congress to fund the wall.
“I think it is bad for a Republican senator — I also think it is bad for a Democrat senator — to vote against border security and to vote against the wall,” he said. “I think to vote that way is a very bad thing long into the future.”
But Republicans are struggling with the vote. Conservatives such as Mr. Lee and Senator Rand Paul of Kentucky — another Republican who says he will vote for the resolution of disapproval — believe that members of Congress have ceded far too much power to the executive branch over the years in an effort to avoid taking politically tough stances themselves. Republicans regularly accused President Barack Obama of executive overreach on issues such as immigration, health care and the environment and now risk being accused of hypocrisy if they stand by while Mr. Trump ignores Congress to do as he wishes.
Many Republicans believe that allowing Mr. Trump to redirect money at his own discretion after Congress explicitly forbade it would amount to a final acquiescence to the executive branch that could set a precedent for future Democratic presidents. But they are also in no rush to irritate a president who has shown vast capacity to stir Republican voters or to rile the activist groups that back him.
On Wednesday, The Hill newspaper reported that conservative groups such as the Club for Growth were considering backing a primary challenge next year to Senator Thom Tillis, Republican of North Carolina, because of his opposition to Mr. Trump on the emergency declaration and other issues.