WASHINGTON — By the time the Senate opened impeachment trials for Andrew Johnson and Bill Clinton, its members pretty well knew the facts of the accusations against the presidents. None of them needed to turn on “The Rachel Maddow Show” to learn things they did not already know.
But as senators formally convened on Thursday as a court of impeachment in the case of Donald John Trump, new revelations were still emerging and important questions remained unanswered. The latest interviews by Lev Parnas, the Soviet-born associate of Rudolph W. Giuliani, the president’s personal lawyer, as well as documents released by House investigators, only reinforced the reality that there is more still to be learned.
None of it may matter to the outcome even if more information does present itself in the weeks to come. The quasi-jurors who swore an oath on Thursday to do “impartial justice” for the most part have already signaled their partiality. And what has been documented so far gives a pretty clear picture of Mr. Trump’s efforts to pressure Ukraine for incriminating information about his political rivals, whether it is cause for removing him from office or not.
Yet there are still so many loose threads to be pulled that the story feels incomplete. Did Mr. Trump know “everything that was going on,” as Mr. Parnas put it in an interview with The New York Times on the same day he appeared on Ms. Maddow’s MSNBC show? Was an American ambassador who had been targeted by Mr. Trump really put under surveillance by an unstable associate of Mr. Parnas, as text messages indicated?
Underscoring the fluidity of the story was the release on Thursday of a damning new report by the independent Government Accountability Office, or G.A.O. The report concluded that the federal budget office, acting on Mr. Trump’s orders, violated federal law by suspending security aid to Ukraine even as the president and his associates were pushing the former Soviet republic for help against Democrats. The accountability office’s finding would presumably be relevant in a trial turning in part on the suspended aid.
And the recent offer to testify by John R. Bolton, the president’s former national security adviser who privately denounced the geopolitical “drug deal” orchestrated by Mr. Trump’s other advisers, only underlines that many of the key players in the tale of intrigue have yet to publicly disclose what they know.
The missing information, like almost everything else in Washington these days, is seen through drastically different lenses depending on the viewer’s political perspective.
To Democrats, Mr. Parnas’s revelations and Mr. Bolton’s offer of testimony only bolster their argument for calling witnesses during the Senate trial, which will get underway in earnest on Tuesday. If the Republican majority led by Senator Mitch McConnell of Kentucky refuses, Democrats say, it will be perpetuating a cover-up on behalf of a corrupt president.
“Both the revelations about Mr. Parnas and the G.A.O. opinion strengthen our push for witnesses and documents in the trial,” Senator Chuck Schumer of New York, the Democratic leader, told reporters. “The G.A.O. opinion, especially, makes clear that the documents we requested in our letter to Leader McConnell are even more needed now than when we requested it last month. Because President Trump, simply put, broke the law.”
To Republicans, the latest claims and disclosures are evidence that House Democrats put together a slapdash investigation that was not thorough enough before they rushed to an ultimately partisan vote on the House floor. It is not the Senate’s job, Republicans say, to do what the House failed to do.
“Makes them look sloppy as hell,” said Solomon L. Wisenberg, a deputy independent counsel during the investigation that led to Mr. Clinton’s impeachment and trial 21 years ago. “I think they should have gotten their act together a little better.”
Mr. Wisenberg said the House Democrats should have authorized an impeachment inquiry earlier and issued subpoenas to Mr. Bolton and anyone else they wanted to question. “They wouldn’t be in this hot mess,” he said.
One way or the other, it is clear the Senate is opening a trial in a far different position than it did in 1868 when it determined Johnson’s fate or in 1999 when it considered charges against Mr. Clinton, both of whom were ultimately acquitted.
The Johnson case turned largely on two allegations — that he improperly fired the secretary of war and that he maligned Congress in a series of speeches. In neither instance were the facts seriously in question, only the legitimacy of his actions.
With Mr. Clinton, every significant possible witness had been interviewed by the investigators of the independent counsel Ken Starr before Congress took up the issue, and the question before the Senate was really about interpreting the facts and deciding whether they added up to high crimes worthy of removal from office.
With Mr. Trump, there was no special prosecutor investigating the Ukraine matter so it was left to the House itself to unearth the details of what happened. But the president refused to turn over documents and tried to block testimony by current and former advisers. That led Democrats to make the strategic decision not to wait for a prolonged court fight to force key witnesses like Mr. Bolton to testify, reasoning that the evidence they had already turned up was enough to justify articles of impeachment. But they said that decision should not stop the Senate from trying to get to the truth.
In the Clinton case, the fight focused on witnesses who had already testified during Mr. Starr’s grand jury and they had no new information to provide during the Senate trial. Refusing to hear from Mr. Bolton or others who have never testified like Mick Mulvaney, the acting White House chief of staff, means senators would decide guilt or innocence without access to the fullest version of the facts.
After complaining in the House that the witnesses who testified generally offered secondhand or hearsay accounts, Republicans would now be in the position of turning down testimony from advisers who do have firsthand information.
“It seems evident the Senate will have to call witnesses if they are going to uncover the rest of the story,” said Byron L. Dorgan, a Democrat from North Dakota who was a senator during the Clinton trial.
Still, there is risk involved for Democrats prosecuting the president. Mr. Parnas in some ways mainly amplifies what is already known from other evidence and to the extent that he adds to the case against Mr. Trump, his credibility could be attacked given that he has been indicted on campaign finance charges.
As for Mr. Bolton, no one knows for sure what he would say if he did testify. While he was described as critical of the Ukraine pressure campaign by other officials, it is not known whether he would implicate or exonerate the president himself. He left the White House on acrimonious terms and has criticized some of the president’s foreign policy decisions, but he has not become a Never Trumper-style critic and some Democrats are privately nervous about his potential testimony.
Even if they do not end up with the witnesses and documents they want, Democrats argue that the latest revelations from Mr. Parnas and the G.A.O. report indicate that the House charges were on track.
“Everything we’re hearing now demonstrates that the House did get it right,” said Robert F. Bauer, a New York University law professor who was the chief lawyer for Senate Democrats during the Clinton trial. “Contrary to the allegations the Senate has made, what emerges here is confirmation that the House articles are well founded.”
Still, it may not make much of a difference in the end anyway. Most of the senators and most of the public seem to have made up their minds about Mr. Trump’s actions; from the time the House hearings started, polls showed Americans almost evenly divided and their views were not changed by the testimony one way or the other.
Some Republicans said more information would not affect the bottom line, which is that in their view the articles of impeachment simply do not add up to high crimes and misdemeanors and would lower the bar for future presidents. More text messages from Mr. Parnas or legal complaints about the process used to suspend the aid, they said, would not change that.
“My view is that whatever the facts, these two articles are so subject to future abuse that the Senate should dismiss them on their face,” said John C. Danforth, a moderate Republican from Missouri who served in the Senate. “This comes from a Republican who has been openly critical of Trump.”