The Senate voted to bar new evidence in the impeachment trial Friday, paving the way for President Trump’s acquittal even as several top Republicans acknowledged that his actions toward Ukraine were not appropriate.

Eleven days into the trial, the highly anticipated vote, which was decided 51 to 49, revealed the partisan divisions in the chamber over whether to subpoena witnesses and documents, a step Democrats argued was crucial to weighing whether Trump abused his power in pressuring Ukraine to announce investigations of his political rivals. Among Republicans, only Sens. Susan Collins (Maine) and Mitt Romney (Utah) supported the resolution.

In declining to add to the case presented by House Democrats, the Senate delivered a victory for the White House that all but guaranteed that Trump will remain in office. With a final vote on the articles of impeachment set for Wednesday at 4 p.m., Democrats argued that Trump’s expected acquittal will be illegitimate, an acknowledgment of their looming defeat.

“If [a] judge or president believes that it is to his or her advantage that there shall be a trial with no witnesses, they will cite the case of Donald Trump,” said Rep. Adam B. Schiff (D-Calif.), one of the House impeachment managers. “They will make the argument that you can adjudicate the guilt or innocence of the party without hearing from a single witness, without reviewing a single document. . . . I would submit that will be a very dangerous and long-lasting precedent that we will all have to live with.”

Soon the questions surrounding Trump’s actions toward Ukraine will move from the Senate floor to the campaign trail, where voters instead of lawmakers will weigh the evidence in the heat of the 2020 presidential election.

House Democrats have promised to continue investigating Trump, and new, potentially damaging information could emerge as it has at times during the trial from an indicted former associate of Trump’s personal attorney Rudolph W. Giuliani and a forthcoming book by John Bolton, the former national security adviser.

But on Friday, Senate Republicans said they had finished weighing the matter — united in their decision to move on, even if members offered varying and at times conflicting reasons for their impending votes to acquit.

Trump is accused of withholding military aid and an Oval Office meeting to push Ukraine’s leaders into announcing probes of Democrats, including former vice president Joe Biden, now a presidential candidate, and his son Hunter. The House impeached Trump in December on two counts — abuse of power and obstruction of Congress.

Senate Minority Leader Charles E. Schumer (D-N.Y.) called the result of the trial “one of the worst tragedies that the Senate has ever overcome.”

“Americans will know that this trial was not a real trial. It had no witnesses, no documents,” Schumer told reporters after the vote. “It is a tragedy on a very large scale.”

As the Senate concluded its business for the weekend, Trump accused Democrats of “scamming America.”

“The Radical Left, Do Nothing Democrats keep chanting ‘fairness’, when they put on the most unfair Witch Hunt in the history of the U.S. Congress,” he tweeted.

The Senate approved a resolution setting up closing arguments Monday. Senators will have an opportunity to give speeches Monday, Tuesday and Wednesday about how they plan to vote.

Postponing the final stage of the trial until next week will allow senators to have a full weekend and was a relief for many who have complained about long hours and uncomfortable conditions in the Senate chamber.

But extending the timetable into next week also means the trial will collide with two other major events on the political calendar — the Iowa caucuses on Monday, in which four Democratic senators are competing, and Trump’s State of the Union address on Tuesday night. Senate Majority Leader Mitch McConnell (R-Ky.) called Trump on Friday evening to brief him on the updated timetable, and the president signed off on it, according to an official familiar with the conversation.

Trump left for Mar-a-Lago, his Florida estate, on Friday afternoon without taking questions from reporters.

The impeachment managers’ effort to persuade Republicans to support calling witnesses was confirmed as a failure earlier in the day when pivotal swing vote Lisa Murkowski (R-Alaska) said she would oppose the motion.

In a sharply worded statement, Murkowski decried the impeachment process that started last fall in the House, while declining to weigh in on Trump’s actions.

“Given the partisan nature of this impeachment from the very beginning and throughout, I have come to the conclusion that there will be no fair trial in the Senate,” Murkowski said. “I don’t believe the continuation of this process will change anything. It is sad for me to admit that, as an institution, the Congress has failed.”

Murkowski could have provided the third vote for witnesses, which would have resulted in a 50-50 outcome. Democrats were pushing for Chief Justice John G. Roberts Jr., who is presiding over the trial, to weigh in at that point and permit witnesses or other evidence rather than let the motion fail on the tied vote. But he said Friday that he would not intervene.

“I think it would be inappropriate for me, an unelected official from a different branch of government, to assert the power to change that result so that the motion would succeed,” he told senators.

While Murkowski said her decision was based on her distaste for the process, other Republicans acknowledged to varying degrees that the president was culpable — a shift in position for some that distanced them from the White House and served as an attempt to inoculate themselves if new incriminating details emerge.

Among the Republicans who argued Trump’s behavior was wrong or problematic but not impeachable were Sens. Marco Rubio (Fla.), Rob Portman (Ohio), Patrick J. Toomey (Pa.) and Lamar Alexander (Tenn.).

“Just because actions meet a standard of impeachment does not mean it is in the best interest of the country to remove a President from office,” Rubio wrote Friday in a Medium post.

“I believe that some of the president’s actions in this case . . . were wrong and inappropriate,” Portman said Friday in a statement. “But I do not believe that the president’s actions rise to the level of removing a duly-elected president from office.”

Alexander told The Washington Post on Friday, after announcing the previous night that he would not support calling witnesses, that “there’s a difference between inappropriate conduct, which that clearly is, and treason, bribery, high crimes and misdemeanors. There’s a big gap between this conduct and impeachable conduct.”

Senate Minority Whip Richard J. Durbin (D-Ill.) said he had hoped Alexander would have a “Howard Baker moment,” referring to the Tennessee Republican senator who played a key role in ending Richard M. Nixon’s presidency during Watergate and for whom Alexander was a protege.

“But it appears he will not,” Durbin said.

Republicans staked out their positions as new revelations from Bolton’s unpublished manuscript seemed to undercut key elements of Trump’s defense.

The New York Times reported Friday that Bolton writes in his forthcoming book that Trump told him in early May to call newly elected Ukrainian President Volodymyr Zelensky and ask him to meet with Giuliani, who was pushing for investigations into the Bidens and a widely contested theory that Ukraine worked with Democrats to undermine Trump during the 2016 election.

The directive to Bolton was reportedly given during a meeting that included Giuliani, acting White House chief of staff Mick Mulvaney and White House Counsel Pat Cipollone, who has led Trump’s defense on the Senate floor. If true, it would represent the earliest reported example of Trump’s direct involvement in the pressure campaign against Ukraine.

Trump denied the report in a statement, saying the meeting “never happened.”

But Schiff seized on it in making his argument for witnesses.

“The facts will come out,” he said. “They will continue to come out. And the question before you today is whether they will come out in time for you to make a complete and informed judgment as to the guilt or innocence of the president.”

Also citing Bolton’s manuscript, the Times reported Sunday that in a conversation with Bolton in August, Trump directly tied his hold on $391 million of military aid to investigations into Democrats.

New revelations have also come from Lev Parnas, the ex-Giuliani associate now facing campaign finance charges, who submitted a letter to McConnell on Friday offering to testify about his participation in an effort to oust former U.S. ambassador to Ukraine Marie Yovanovitch and gather damaging information about Joe and Hunter Biden.

The letter, written by Parnas’s lawyers, stated that the efforts involved a large group of top Republican officials and operatives, including Vice President Pence, then-Energy Secretary Rick Perry, Secretary of State Mike Pompeo, Attorney General William P. Barr, Sen. Lindsey O. Graham (R-S.C.) and Rep. Devin Nunes (R-Calif.).

Parnas had disclosed much of the information included in the letter in recent media interviews. His claims have been disputed by various Republican leaders, including Pence and Barr.

Trump’s former chief of staff, John F. Kelly, who said earlier in the week that he believed Bolton, called the Senate trial “half a trial” if no witnesses are called.

“In my view, they kind of leave themselves open to a lot of criticism,” Kelly said in an interview with N.J. Advance Media. “It’s a job only half done. You open yourself up forever as a Senate that shirks its responsibilities.”

As Friday night drew to a close, it appeared Trump would deliver his State of the Union address before his expected acquittal, a small messaging coup for Democrats that was played down by the White House.

“The president is gratified that finally, at long last, after multiple delays, the Senate will set a schedule for his acquittal next week,” said White House director of legislative affairs Eric Ueland. “We do not believe the schedule interferes with his ability to deliver a strong and confident State of the Union message next week in the House of Representatives to the country.”

Meanwhile, the four senators running for president eagerly recast their schedules to take advantage of the free weekend.

“Are you going to Iowa?” a reporter shouted to Sen. Amy Klobuchar (D-Minn.), one of the candidates, at the Capitol on Friday night.

“Eventually!” she said.

Colby Itkowitz, Paul Kane, Rosalind S. Helderman, John Wagner and Michael Brice-Saddler contributed to this report.