Senate Minority Leader Charles E. Schumer on Thursday evening backed off his shutdown threat and said he will vote to end a filibuster of the Republicans’ spending bill, providing a list of arguments that gave a green light to other Senate Democrats to do the same.

Mr. Schumer, New York Democrat, effectively caved to Republicans’ wishes after failing to convince them that a one-month stopgap spending bill was preferable to the GOP plan to extend current funding levels — with a handful of exceptions — through the Sept. 30 end of the fiscal year.

“It’s a Hobson’s choice, either proceed with the bill before us or risk Donald Trump throwing America into the chaos of a shutdown,” he said.

He rationalized that while the GOP bill “is very bad, the potential for a shutdown has consequences for America that are much, much worse.”

Sen. John Cornyn, Texas Republican, called Mr. Schumer’s pivot a “full cave” and said other Democrats would “fall in line.”

Mr. Schumer’s decision came after days of private discussions with his caucus wrestling over whether to back the GOP bill, which passed the House on Tuesday with all but one Democrat voting in opposition.

The Senate’s initial procedural test vote is scheduled for early Friday afternoon. It will take a time agreement from all 100 senators to speed through other procedural hurdles and pass the bill before the midnight deadline. 

Senate Republicans have a 53-seat majority but need 60 votes to clear a filibuster. Kentucky GOP Sen. Rand Paul is opposed to the measure, which means the bill needs support from at least eight Democrats to survive and to avoid a shutdown.

While Senate Democrats are wary of shutting down the government, many believed voting against the measure is their only way to stand up to President Trump and his cost-cutting Department of Government Efficiency.

“I think when you confront a bully, you have to confront a bully,” said Sen. Martin Heinrich, New Mexico Democrat.

Mr. Heinrich and other Democrats who decided to oppose the GOP stopgap said they did not want to enable Mr. Trump and DOGE to further ignore government spending directives as they slash the government bureaucracy. But they acknowledged a shutdown would have similarly devastating consequences for government workers and Americans who rely on federal programs.

“This president has put us in a position where, in either direction, lots of people’s constituents are going to get hurt and hurt badly,” Mr. Heinrich said. “So people are wrestling with what is the least worst outcome.”

On Wednesday, Mr. Schumer said his caucus was united against the GOP plan and would not provide Republicans with enough votes to overcome a filibuster because they were not included in drafting the bill.

Republicans had already started a social media campaign attacking Democrats for the “Schumer shutdown.”

If the Democratic leader proceeded with his initial plan to block the bill, the government would have shut down after midnight Friday, save for services that the Trump administration deems essential.

In reversing course, Mr. Schumer decided that giving the president that power “is a far worse option” than the GOP stopgap.

“A shutdown would give Donald Trump and Elon Musk carte blanche to destroy vital government services at a significantly faster rate than they can right now,” he said, noting that federal workers would be furloughed with no promise of being rehired.

Mr. Schumer also argued that a shutdown could stall federal court cases Democratic groups are leading against DOGE’s actions, which he called one of the best options for fighting back against the president’s lawlessness.

“And make no mistake, Democrats will continue to fight what Donald Trump is doing,” he said.

Before Mr. Schumer’s remarks, the only Democrat backing the GOP plan was Pennsylvania Sen. John Fetterman, who says he “will never vote to shut the government down.”

The GOP bill is the third government funding stopgap, known as a continuing resolution or CR, for the fiscal year that started last Oct. 1. This latest CR would extend most fiscal 2024 spending levels and policies through the end of fiscal 2025 on Sept. 30.

The measure includes some exceptions to the flat funding, like $13 billion in cuts to nondefense spending on projects lawmakers requested for their districts, increases of $6 billion each for defense spending and veterans’ health care and a roughly half a billion-dollar bump for the U.S. Immigration and Customs Enforcement, which has been running low on funding for detention and deportation of unauthorized immigrants.

Senate Democrats prefer a shorter, one-month CR through April 11, which they said would buy enough time to finish bipartisan negotiations on new spending levels and policies and pass fiscal 2025 appropriation bills. Appropriators were close to a “top-line” deal on spending levels but negotiations stalled over Democrats’ demands to include language restricting the president from ignoring congressional spending directives.

“We’re this close to getting a bipartisan bill, so why wouldn’t we do that?” Sen. Raphael Warnock, Georgia Democrat, told The Washington Times.

He did not say whether he would support a procedural vote on the GOP bill, but others said they would not help end a filibuster.

That includes Sens. Chris Van Hollen and Angela Alsobrooks of Maryland and Mark R. Warner of Virginia, who represent scores of government workers who would be furloughed under a shutdown.

Ms. Alsobrooks said the GOP stopgap would enable Mr. Trump to continue a “witch hunt against our patriotic civil servants — people who work on behalf of our veterans, people who work on behalf of our students, people who work on behalf of our domestic violence survivors.”

“We have a unique opportunity at this moment to course correct and pass a clean, bipartisan funding bill that would address some of these concerns and mistakes,” she said.

Other Democrats who say they won’t help pass the GOP stopgap bill include senators from states Mr. Trump won in the presidential election, such as Sens. Ruben Gallego and Mark Kelly of Arizona.

“I told Arizonans I’d stand up when it was right for our state and our country, and this is one of those moments,” Mr. Kelly said.