WASHINGTON — House Democrats were prepared and passionate as they laid out over three draining days in the Senate a detailed argument for impeaching and removing President Trump. What they do not appear to have been is persuasive to the critical handful of Republicans who hold the key to their immediate objective: gaining access to witnesses and documents that could cement their case.
While Senate Republicans commended Democrats for a thorough and mainly respectful presentation, they gave no indication as the arguments drew to a close that they were ready to expand the scope of the trial, let alone to vote to remove Mr. Trump from office at the end of it. The sense in the Capitol was that the trial was heading toward its predictable conclusion, Mr. Trump’s acquittal, as early as next week.
It has always been only a small group of Republicans who were truly considered possible defectors who might join Democrats on the volatile issue of seeking witnesses in the trial. Senators Susan Collins of Maine and Mitt Romney of Utah have been the most forward-leaning of the Republicans who have expressed openness to the idea. But their ranks appeared to be thinning this week.
Senator Lamar Alexander, Republican of Tennessee, who had signaled potential interest in considering new evidence, said on Friday he would wait until after the president’s defense and senators have time to question the lawyers to make his decision, but he did not sound eager to push the proceeding into the unknown.
“As the House managers have said many times, they’ve presented us with a mountain of overwhelming evidence, so we have a lot to consider already,” he told reporters.
Another possible vote for witnesses, Senator Lisa Murkowski of Alaska, also sounded reluctant on Thursday, citing an argument being made by the president’s legal team and her more conservative colleagues against extending the trial.
“The House made a decision that they didn’t want to slow things down by having to go through courts,” Ms. Murkowski said. “And yet now they’re basically saying ‘You guys — the Senate — got to go through the courts. We didn’t, but we need you to.’”
And on Friday, when Representative Adam B. Schiff, the lead House manager, referred to a news report that Republican senators had been warned that their heads would be “on a pike” if they strayed from Mr. Trump, Ms. Collins and Ms. Murkowski were among those visibly outraged.
Polls show that the public, including a large proportion of independents and even Republicans, is increasingly supportive of hearing new evidence. But for Democrats, persuading Republicans in the Senate was always a tall order.
Republicans have long argued that the Democrats’ main aim is to use impeachment to increase their chances of winning the White House, holding the House and seizing the Senate this fall by energizing their voters, independents and Republicans uncomfortable with Mr. Trump while putting endangered Senate Republicans in the hot seat. That has irritated Republicans, sharpening their determination to stick together and push back against the efforts to prolong the trial.
“There has never been a likelihood in a partisan impeachment that you would remove the president, so you have to look at what else it might be about,” said Senator Roy Blunt of Missouri, a member of the Republican leadership. “And it is all about politics.”
Democrats vigorously dispute that claim. Senator Chuck Schumer of New York, the party leader, said at the start of the week that Democrats were only doing their constitutional duty and were not motivated by political gain.
Still, while Democrats might be loath to acknowledge it publicly, a clear subtext of the trial was the opportunity to portray Mr. Trump as unfit for office, and indeed dangerous. If Republican senators refused to recognize that, if they were willing to look the other way and tolerate his behavior, they argued in stark terms as they stood in the Senate chamber this week, then they should be ousted from office as well.
“The American people deserve a president they can count on to put their interests first,” declared Mr. Schiff, in an emotional speech on Thursday night that sounded as much like a broadside delivered from a podium at a presidential nominating convention as an oral argument given from the well of the Senate during a rare impeachment trial.
His comments and delivery drew effusive praise from those who sided with him. But if those words were meant to stir Senate Republicans to entertain the idea of summoning administration officials to testify before the Senate, they fell far short.
Multiple Republican senators said they were offended by Mr. Schiff’s pointed portrayal of the president as a craven politician who would always put himself before the public, which suggested that they, by declining to condemn him, were failing in their duty as well.
Republicans added the Democrat’s comments to their ever-expanding list of reasons to oppose extending the proceedings by demanding budget documents and subpoenaing witnesses such as Mick Mulvaney, the acting White House chief of staff, and John R. Bolton, the former national security adviser.
Many Republicans — after four days of being confined to the Senate chamber with more to come — said they had heard enough, and heard it over and over again as the House Democrats used repetition to hammer home the claim that Mr. Trump’s actions in pushing Ukraine to investigate a political rival while he withheld military aid merited his ouster.
“It became mind-numbing after a while,” said Senator Lindsey Graham, Republican of South Carolina.
While the repetition was exasperating to Republican senators, it may have been beneficial to Democrats. For in arguing their case against the president, Democrats were appealing not only to reluctant Senate Republicans but to an American public still absorbing and processing the accusations against the president. While the Senate verdict could come soon, the public judgment will not be rendered until November.
And while Democrats might not reach their overarching goal of ousting the president before the election, they have had some political success in the trial, notably forcing Senate Republicans to take a series of tough votes at the start of the proceedings.
One thing Senator Mitch McConnell, Republican of Kentucky and the majority leader, is always eager to avoid is having his embattled incumbents put on the spot. Through his control of the floor, he is usually able to do so.
But in the framework of the impeachment trial, he could not stop Democrats, who forced Republicans to vote not just against witnesses but against specific ones such as Mr. Mulvaney and Mr. Bolton.
“This is about Susan Collins,” Senator John Barrasso of Wyoming told reporters as he listed the names of embattled Republicans from North Carolina, Arizona and Colorado who, like Ms. Collins, are facing voters this fall. “This is about Thom Tillis. This is about Martha McSally. This is about Cory Gardner.”
“Only part of it is removing President Trump and taking his name off the ballot,” Mr. Barrasso added. “It is also about Chuck Schumer trying to make himself a majority leader of the United States Senate, and there’s no way to deny it.”
Republicans said the president’s record and conduct should be a matter for voters to deal with in November, not by the Senate in January.
“As to Mr. Schiff’s discussion about why we need to remove the president, I think you saw in there some animosity toward this president that needs to be resolved at the ballot box, not in the court of impeachment,” Mr. Graham said.
In some ways, Democrats have always known that would be the ultimate resolution. While they might lose in the trial, they hope their prosecution helps deliver them wins in November.