WASHINGTON — Just after President Donald Trump’s defense lawyers ended arguments in their Senate trial Tuesday, Sen. Dianne Feinstein suggested she could vote to acquit him, despite serious concerns about his character.

“Nine months left to go, the people should judge. We are a republic, we are based on the will of the people — the people should judge,” Feinstein said Tuesday, after the president’s team finished a three-day presentation in his defense. “That was my view and it still is my view.”

Still, she indicated that arguments in the trial about Trump’s character and fitness for office had left her undecided. “What changed my opinion as this went on,” she said, is a realization that “impeachment isn’t about one offense. It’s really about the character and ability and physical and mental fitness of the individual to serve the people, not themselves.”

Asked whether she would ultimately vote to acquit, she demurred, saying, “We’re not finished.”

After those remarks were published, Feinstein issued a statement saying she had been misunderstood.

“Before the trial I said I’d keep an open mind. Now that both sides made their cases, it’s clear the president’s actions were wrong. He withheld vital foreign assistance for personal political gain. That can’t be allowed to stand.”

Feinstein’s original remark went further than any of her fellow Democrats in suggesting that she might vote for acquittal. Several Democrats have not ruled out voting for acquittal. But only two Democrats were considered truly up for grabs because of the strong support for Trump in their states: Sens. Joe Manchin of West Virginia and Doug Jones of Alabama.

Manchin told CNN on Saturday that Trump’s team did a “good job” in its initial arguments, “making me think about things.” He said separately on Fox, “I am totally undecided.”

Feinstein’s comments came after final arguments from Trump lawyers in which they broadly dismissed the elephant in the Senate chamber: a leaked firsthand account from John Bolton, the former national security adviser, that the president directly tied aid to Ukraine to his demands for the country to investigate political rival Joe Biden.

Feinstein told reporters that her office had received roughly 125,000 letters in support of the impeachment last week, and about 30,000 against it. “There is substantial weight to this,” she said, “and the question is: Is it enough to cast this vote?”

The revelation Sunday from a draft manuscript of Bolton’s upcoming book undercut the president’s defense and splintered Republicans, leaving a few of them calling for Bolton and other witnesses to testify. GOP leaders have opposed calling witnesses, which would prolong the trial and introduce potentially damning testimony, upending White House and Senate Republicans’ plans for Trump’s quick acquittal.

The trial is heading into a crucial stage. On Wednesday senators are planning to start their public questioning of both the defense team and the Democratic House impeachment managers, with key votes on whether to call witnesses. The outcome of a vote on allowing witnesses, expected Friday, remained uncertain after a closed-door strategy session of Senate Republicans on Tuesday afternoon. “No clear conclusions,” said Sen. Mike Braun, R-Ind.

After the Trump team initially sidestepped the Bolton reports in their arguments Monday, Trump lawyer Jay Sekulow urged the Senate on Tuesday to ignore the recent reports.

Impeachment, Sekulow said, “is not a game of leaks and unsourced manuscripts. That is politics unfortunately.” Alexander Hamilton, he continued, “put impeachment in the hands of this body, the Senate, precisely and specifically, to be above that fray.” The Senate, Sekulow said, should “end the era of impeachment for good.”

Alan Dershowitz, a veteran defense attorney, was the only member of Trump’s 10-person team to mention Bolton’s name Monday, the first full day of the lawyers’ presentation. While Trump has argued that his July 25 call with the Ukrainian president that prompted the impeachment inquiry was “perfect,” Dershowitz at one point suggested a different defense tack, arguing essentially, so what?

“Nothing in the Bolton revelations, even if true, rise to the level of an abuse of power or an impeachable offense,” Dershowitz told the Senate in his first appearance at the trial.

Sen. John Cornyn, R-Texas, echoed that argument Tuesday, suggesting that even if Democrats could get the necessary four Republican votes for a majority in favor of subpoenaing Bolton or other witnesses, it wouldn’t make much of a difference given that the Republican-majority Senate will almost certainly vote to acquit the president.

“To me, it seems like the facts are largely undisputed; I don’t know what additional witnesses will tell us,” Cornyn said of Bolton. “We know what the facts are, and the question is whether the facts meet the constitutional standard of ‘high crimes and misdemeanors.’”

Trump’s lawyers have continued to assert that Trump had “done nothing wrong” and was genuinely interested in combating corruption in Ukraine when he directed that nearly $400 million in security assistance and a White House meeting with its president be withheld as he pushed the new government to announce probes of Biden and his son Hunter Biden. Hunter Biden served on the board of a Ukrainian energy company when his father was vice president.

The president’s lawyers have said that House Democrats didn’t provide any firsthand witnesses or direct evidence to prove their charges that Trump abused his power by pressuring Ukraine to investigate his potential rival in the 2020 presidential election and then obstructed Congress to cover it up.

Bolton, a combative conservative and a hawk on national security, declined a House invitation to testify but subsequently said he would do so at the Senate trial if subpoenaed. However, the White House issued a blanket order blocking officials and documents, calling the impeachment process illegitimate.

The Bolton allegations have fractured the largely united front that Senate Majority Leader Mitch McConnell, R-Ky., had maintained. Several mostly moderate Republicans who had been open to calling witnesses have now become more so.

Sen. Mitt Romney, R-Utah, made an impassioned speech during a party lunch Monday arguing for Bolton to be called, leading to a direct attack from colleague Sen. Kelly Loeffler, R-Ga. Afterward, Romney told reporters that “it’s increasingly likely” that there will be enough votes to subpoena Bolton.

Underscoring the chaos the Bolton report has unleashed, other once-resistant Republicans seemed to shift their position on witnesses.

Sen. Lindsey Graham, R-S.C., one of the president’s closest allies in the Senate, initially opposed calls for any witnesses, whether the Bidens or Bolton. He seemed to reverse himself Monday after the Bolton reports, and Tuesday he supported a proposal by Sen. James Lankford, R-Okla., that Bolton’s manuscript be made available for senators to read in a classified setting known as a SCIF, or Sensitive Compartmented Information Facility. The idea could be viewed as a way of getting Bolton’s information to the Senate without his public testimony.

Each senator would have “the opportunity to review the manuscript and make their own determination,” Graham tweeted.

Sen. Charles E. Schumer, D-N.Y., the Senate minority leader, rejected the proposal as “absurd.”

“It’s a book,” Schumer said of Bolton’s manuscript, which is set to publish in March. “There’s no need for it to be read in the SCIF unless you want to hide something.”

Sen. Rand Paul, R-Ky., questioned Bolton’s motivations for wanting to testify, and the timing of the leak. “Democrats have spent a lot of time imagining what the president’s motives are,” Paul said. “Someone ought to spend some time imaging what John Bolton’s motives are other than making millions of dollars to trash the president.” And Sen. Roy Blunt, R-Mo., quipped, “I’m sure Mr. Bolton would rather I’d bought the book.”

Other Republican senators indicated they would continue taking their cue from the president’s team. Pam Bondi, a former Florida attorney general, pushed unproved theories that the Bidens engaged in corruption in Ukraine. Kenneth W. Starr, the prosecutor whose four-year investigation ultimately led to the impeachment of Democratic President Bill Clinton, claimed that the impeachment process itself is being abused for political ends.

As Trump’s defense team wrapped up, the war over witnesses is likely to be reflected in senators’ written questions to the president’s lawyers and the Democratic House managers. They have up to 16 hours on Wednesday and Thursday for questions, which will go back and forth between Republicans and Democrats, to be read aloud by Chief Justice John G. Roberts Jr.

Roberts said on Tuesday that lawyers on both sides should adhere to Chief Justice William Rehnquist’s guidelines in the Clinton trial of a five-minute cap on answers.

Sen. Richard J. Durbin, D-Ill., the Senate minority whip, said he had whittled his nearly 30 questions down to nine. Democratic leaders have collected draft questions to “avoid duplication and pick the ones in sequences that make sense in terms of delivering a message,” he said. Schumer said Democrats’ questions would give House managers a chance to rebut the Trump lawyers’ claims.

Several questions are expected about Bolton, with Republicans focusing on why the House didn’t push harder to get his testimony. Both Republicans and Democrats have also suggested they have questions about Rudolph W. Giuliani, the president’s personal lawyer, who was central to the dealings in Ukraine.

“I want to confirm that Rudy Giuliani was working personally for the president and not on behalf of the United States of America,” said Jones, the Alabama Democrat.

Manchin has said he would also like to hear from Trump’s White House chief of staff Mick Mulvaney, based on testimony during the House impeachment investigation about his dealings with Trump on Ukraine policy.

It remains unclear what sort of agreement Republicans and Democrats could reach on calling witnesses, with additional testimony carrying risks for both sides. Many Republicans have said they would agree to calling Bolton only if the Bidens are also subpoenaed, while Democrats say they won’t be any part of any such “trade,” because the Bidens are irrelevant to the charges against Trump.

“I’ll make a prediction: (There will) be 51 Republican votes to call Hunter Biden, Joe Biden, the whistleblower,” Graham warned. “If people want witnesses, we’re going to get a lot of witnesses.”

Durbin called the idea of bargaining over testimony — “‘Well, we’ll give you one material witness for one relevant witness’” — “baloney.” Sen. Christopher S. Murphy, D-Conn., said that agreeing to call Biden in exchange for Bolton would make Democrats “complicit” in Trump’s original scheme to smear Biden.

Sen. Kevin Cramer, R-N.D., argued Tuesday morning against any witnesses. “When you open the door a little you’ll never satiate the appetite that House managers have for witnesses,” Cramer said. “It’s as though they want to go fishing in the United States Senate and they’re going to fish until they catch one.”