Senate Republicans defeated an effort by Democrats to bar President Trump from establishing a fund that could compensate his political allies, as they kicked off a slog of votes on their immigration crackdown bill that stretched into early Friday.
The vote came as the G.O.P. worked to push through their $70 billion bill to fund immigration enforcement for the remainder of Mr. Trump’s term, a top party priority they were eager to spotlight in the middle of an election year as their control of Congress is at stake.
The measure has in recent weeks been imperiled by a rare spate of Republican pushback to Mr. Trump, as G.O.P. lawmakers have revolted over his request for $1 billion to fund his ballroom project and a plan to establish a $1.8 billion fund to pay people who he claims have been victimized by the government.
“This would have been done several hours ago if we weren’t having to deal with some of the issues around the fund,” Senator John Thune, Republican of South Dakota and majority leader, told reporters just before midnight at the Capitol.
Still, as senators voted on amendment after amendment, most Republicans appeared to be swallowing their concerns and uniting to defeat Democrats’ efforts to tie Mr. Trump’s hands on a wide variety of issues.
The first such vote was on a motion by Senator Chuck Schumer, Democrat of New York and the minority leader, to send the immigration bill back to committee and add a prohibition on the creation of the fund. It failed 50 to 49, with three Republicans facing re-election — Senators Susan Collins of Maine, Jon Husted of Ohio and Dan Sullivan of Alaska — joining Democrats in support.
Though the Justice Department has said it will no longer pursue Mr. Trump’s plan to establish a payout fund, the amendment was a bid by Democrats to force Republicans to cast a politically painful vote on the matter. Many Republicans have said that they, too, would like to codify into law that such a fund could not be pursued in the future.
“America has never seen a more clear-cut case of corruption than Donald Trump’s slush fund,” Mr. Schumer said as he introduced his motion.
It also offered a moment of leverage for Republican senators who have expressed concerns about the fund to extract assurances from G.O.P. leaders for amendments they might want to offer to kill the idea for good. They included Senators John Cornyn of Texas, Bill Cassidy of Louisiana, Lisa Murkowski of Alaska and Thom Tillis of North Carolina, all of whom have suggested that Congress should act decisively to block the fund even after Todd Blanche, the acting attorney general, told the House under oath this week that the fund was dead, permanently.
The Senate ground to a halt for hours during the vote, as Republicans crowded together on the floor in deep discussions over how to address the issue.
Ms. Collins cast her “yes” vote early on, after huddling with G.O.P. leaders, who could afford few defections to have enough to defeat the motion and keep their immigration bill on track.
But Mr. Cassidy, Mr. Husted and Mr. Sullivan withheld their votes for hours. Later, Mr. Cassidy told reporters he had been holding out for the best possible deal.
“I just wanted to optimize chances for success,” he said after voting against the measure.
But late Thursday night, Mr. Cassidy was still working with Democrats and Senate officials to devise a proposal to block the fund that could pass with just 50 votes rather than 60. It was not clear whether he would be able to find a path forward to add the proposal to the bill.
Mr. Tillis, who also voted against the Democrats’ initial proposal, told reporters that he and other Republicans were working on a variety of approaches that would “get the fund out” without imperiling the bill. Later, he tried unsuccessfully to redirect $1.8 billion in Justice Department funding to anti-fraud initiatives, a proposal he said was aimed at steering money away from the president’s payout fund.
The jam was exactly what Mr. Schumer had previewed for days as he threatened to use the immigration bill to pin Republicans over the fund, Mr. Trump’s ballroom and an array of other unpopular aspects of his agenda.
Republicans had expressed concern about the administration’s request that the bill include $1 billion for security measures tied to the ballroom, and they stripped it from immigration legislation before it reached the floor.
But on Thursday, they blocked a proposal by Senator Jeff Merkley, Democrat of Oregon, to bar federal funds from being used for the project without congressional approval. Only a handful of Republicans — including Ms. Collins, Mr. Husted, Ms. Murkowski, Mr. Tillis and Mr. Sullivan — backed it, leaving it short of the 60 votes it needed to pass.
Republicans said that the focus on the $1.8 billion fund — which had become a major impediment to passage of their $70 billion immigration enforcement bill even though the measure is silent on the matter — was an effort by Democrats to distract from their opposition to funding ICE and the Border Patrol.
Mr. Thune took to the floor on Thursday morning to try to keep the focus on the immigration bill that was supposed to be a point of unity for the party to rally around. The Senate was expected to vote on it later Thursday.
“We are here today only, only because Democrats refuse to appropriate a single dollar for our border and immigration law enforcement,” Mr. Thune said, referring to Democrats’ refusal to agree to further funding for Mr. Trump’s crackdown without new restrictions on the tactics and conduct of federal agents carrying it out.
That prompted Republicans to turn to a special budget process to move immigration enforcement funding through the Senate in a bill that is not subject to a filibuster, meaning that they can win its approval without a single Democratic vote.
But by midnight, they had considered 16 amendments and were far from finished with an hourslong vote-a-thon more on issues on which Democrats were seeking to put Republicans in a political bind.
