WASHINGTON — The White House and Senate Republicans worked aggressively on Wednesday to discount damaging revelations from John R. Bolton and line up the votes to block new witnesses that would bring President Trump’s impeachment trial to a swift close.
As the Senate entered a two-day, 16-hour period of questioning from senators, Mr. Trump laced into Mr. Bolton, his former national security adviser, whose unpublished manuscript contains an account that contradicts his impeachment defense. The president described Mr. Bolton on Twitter as a warmonger who had “begged” for his job, was fired, and then wrote “a nasty & untrue book.”
Mr. Trump’s aides circulated a letter on Capitol Hill informing Mr. Bolton that the White House was moving to block publication of his forthcoming book, in which he wrote that the president conditioned the release of military aid for Ukraine on the country’s willingness to investigate his political rivals. That is a central element of Democrats’ impeachment case against the president, which charges him with seeking to enlist a foreign government to interfere in the 2020 election on his behalf.
Off the floor, Senator Mitch McConnell of Kentucky, the majority leader, and other Republicans signaled that they were regaining confidence that they would be able cobble together the 51 votes needed to block new witnesses and documents and bring the trial to an acquittal verdict as soon as Friday, after the revelations from Mr. Bolton, reported Sunday by The New York Times, had threatened to knock their plans off course.
By Wednesday afternoon, Democrats were sounding a note of pessimism about the prospect of witnesses and securing new evidence in the trial.
“We’ve always known it will be an uphill fight on witnesses and documents, because the president and Mitch McConnell put huge pressure on these folks,” Senator Chuck Schumer of New York, the Democratic leader, said during a break in the trial.
“Is it more likely than not? Probably no,” Mr. Schumer said. “But is it a decent, good chance? Yes.”
Senator John Barrasso of Wyoming, the No. 3 Senate Republican, declared that he had “heard enough” and predicted that the Senate would vote to acquit the president by week’s end.
“I’m ready to vote on final judgment,” Mr. Barrasso told reporters. Asked if Republicans planned to move directly to a vote on the two articles of impeachment on Friday, Mr. Barrasso said, “Yes, that’s the plan.”
His prediction came as Republican senators appeared to be falling into line to vote against calling witnesses a day after Mr. McConnell warned them privately that he did not currently have the votes to stop Democrats from summoning them. One after the other, in statements and hallway interviews, they made clear they would side with their leader.
Senator Patrick J. Toomey of Pennsylvania, who had previously floated the idea of a witness deal, said Wednesday that he was “very, very skeptical” of new witnesses. Senator Cory Gardner of Colorado, facing a tough re-election in a swing state, issued a statement saying that he had heard enough and would vote against hearing from more witnesses.
And Senator Mitt Romney of Utah, who has said repeatedly that he wants to hear from Mr. Bolton and would vote in favor of witnesses and documents, conceded he did not know how many Republicans would join him.
“I’m sure there’ll be others,” he said. “How many there will be on my side of the aisle, I just don’t know.”
In answering questions, Mr. Trump’s lawyers offered their most expansive defense of the president to date, effectively arguing that a president cannot be removed from office for demanding political favors if he believes his re-election is in the national interest.
“Every public official I know believes that his election is in the public interest,” said Alan M. Dershowitz, the celebrity defense lawyer and constitutional scholar who is part of the Mr. Trump’s legal team. “Mostly, you’re right.”
“If the president does something which he believes will help him get elected, in the public interest, that cannot be the kind of quid pro quo that results in impeachment,” he said.
Mr. McConnell gave his party’s first question on Wednesday to Mr. Romney and Senators Susan Collins of Maine and Lisa Murkowski of Alaska in an effort to allay the concerns of the three lawmakers, Republican moderates who are swing votes on calling witnesses. The trio teamed up to ask Mr. Trump’s lawyers how they should judge the president if they conclude he acted in the Ukraine matter with both political and policy motives.
The selection of Ms. Collins, who is facing the toughest re-election campaign in her long Senate career, was revealing: It suggested that Mr. McConnell was keenly focused on giving her every opportunity to have her voice heard before moving forward.
Notably absent from the group was the fourth Republican who had expressed interest in witnesses: Senator Lamar Alexander of Tennessee, a close friend of Mr. McConnell’s who has said he will not decide whether to support witnesses until after the question period has closed.
Democrats need the votes of four Republicans to compel the Senate to subpoena witnesses and new documents. But it seems increasingly likely that Mr. Alexander, who is retiring from the Senate and is thus free to do as he chooses, will break from his party.
Mr. Trump is charged with abusing his power and obstructing Congress by pressuring Ukraine to investigate his political rivals, including former Vice President Joseph R. Biden Jr. and his son Hunter Biden, and concealing evidence of it from lawmakers who were investigating. Republicans have said that if Mr. Bolton testifies, so too should Hunter Biden, who drew Mr. Trump’s interest because he sat on the board of Ukrainian energy company.
In the first hint of a possible crack in Democratic unity, Senator Doug Jones of Alabama suggested Wednesday that he might vote to acquit Mr. Trump on the charge of obstruction of Congress, though he said that the president’s own behavior was strengthening the case against him. And Senator Joe Manchin III of West Virginia said he thought that Hunter Biden might be a relevant witness.
“I’m still looking at that very closely; there are some things that trouble me about it,” Mr. Jones said, without elaborating. “But I will tell you this about the obstruction charge: The more I see the president of the United States attacking witnesses, the stronger that case gets.”
Fielding friendly questions from Democratic senators, House managers reiterated the heart of their case and accused Mr. Trump’s lawyers of incorrectly stating that there was no evidence that Mr. Trump linked security assistance to investigations. Representative Adam B. Schiff of California, the lead House impeachment manager, responded to Mr. Dershowitz’s argument by saying it was “very odd.”
“If you say you can’t hold a president accountable in an election year where they’re trying to cheat in that election, then you are giving them carte blanche,” Mr. Schiff said. “All quid pro quos are not the same. Some are legitimate and some are corrupt.”
Democrats have argued that Mr. Trump’s pressure campaign on Ukraine was precisely the kind of corrupt scheme that the nation’s founders had in mind when they created impeachment, fearing that an out-of-control executive would abuse his power for personal gain. But throughout the day, lawyers for Mr. Trump argued that all elected officials make policy decisions to help themselves get re-elected.
Answering the question from the three Republican moderates, Patrick Philbin, a deputy White House counsel, said a president could not be removed for a “mixed-motive situation” in which he is acting out of both personal and policy concerns.
“There’s always some personal interest in the electoral outcome of policy decisions and there’s nothing wrong with that,” Mr. Philbin told senators. “That’s part of representative democracy.”
Mr. Trump’s legal team also argued that the House needed to prove its case “beyond a reasonable doubt” — a standard of proof that legal experts say has no basis in either the Constitution or the rules of the Senate. And the legal team said that the case was merely “based on a policy difference” between the president and the career diplomats who sounded the alarm on his pressure campaign in Ukraine.
The questioning is a formal affair: Senators submit questions in writing and they are read aloud by Chief Justice John G. Roberts Jr. The chief justice set a five-minute time limit for answers, citing a similar limit imposed by his predecessor Chief Justice William H. Rehnquist during the impeachment trial of President Bill Clinton in 1999.
White House lawyers have a system to help their speakers stay within the five minutes: a stack of small white cue cards showing when the clock is about to run out. They hold them up when 2 minutes, 1 minute 30 seconds and 10 seconds are left.
The Democratic House members do not appear to have such a system — which may explain why Mr. Schiff was cut off by the chief justice when his first answer ran long.
Catie Edmondson, Nicholas Fandos and Patricia Mazzei contributed reporting.