Special Counsel Robert Mueller broke his almost two-year vow of silence Wednesday to say that he couldn’t reach a conclusion on whether President Donald Trump obstructed justice, but his remarks mostly echoed his voluminous written report and left almost everyone disappointed.

Mueller made clear that he’s not willing to testify to Congress about any details from his investigation into Russian election meddling that weren’t already in the 448-page report, potentially depriving Democrats of additional damaging information about the president.

But the special counsel also underscored that his investigation didn’t clear Trump on the question of obstruction, leaving the president to once again exonerate himself. “The case is closed!” Trump tweeted.

Mueller, who announced that he was closing his office and stepping down from the post of special counsel, said there was insufficient evidence to bring conspiracy charges against anyone involved in Trump’s campaign for interfering in the 2016 election.

“If we had had confidence the president clearly did not commit a crime we would have said so,” Mueller said, defending his investigation as thorough, fair and nonpartisan in a statement at the Justice Department that was his first public comment in the two years since he was named special counsel.

Impeachment Debate

For Democrats, Mueller’s remarks fed into an ongoing debate over whether to open impeachment proceedings. Senator Cory Booker joined several other presidential contenders who have called for the House to move toward impeachment.

In a clear reference to impeachment, Mueller said that Justice Department policy “says that the Constitution requires a process other than the criminal justice system to formally accuse a sitting president of wrongdoing.”

Mueller said he and his investigators were bound by a Justice Department opinion written by the Office of Legal Counsel.

“Under long-standing department policy a president cannot be charged with a federal crime while he is in office. That is unconstitutional,” he said. “Charging the president with a crime was therefore not an option we could consider.”

That appears to contradict what Attorney General William Barr said publicly, when he disputed that Mueller’s decision not to charge Trump was based on the Justice Department policy, written by its Office of Legal Counsel.

Barr told reporters on April 18 that Mueller “made it very clear several times that that was not his position. He was not saying that but for the OLC opinion he would have found a crime," he added. "He made it clear that he had not made the determination that there was a crime."

Mueller’s public appearance only reinforced both sides in the fierce partisan disputes over the report that he completed two months ago on Russian interference in the 2016 election, any links to the Trump campaign and whether Trump sought to obstruct justice.

House Judiciary Chairman Jerrold Nadler, who has been negotiating with Mueller on testifying to his panel, said that “the Constitution points to Congress to take action to hold the president accountable."

“Given that Special Counsel Mueller was unable to pursue criminal charges against the president, it falls to Congress to respond to the crimes, lies and other wrongdoing of President Trump -- and we will do so," Nadler said in a statement that still stopped short on endorsing an impeachment proceeding that would start in his committee.

House Speaker Nancy Pelosi has resisted calls from some members of her party to open impeachment proceedings against the president, which she has argued would be likely to backfire politically and help Trump in his re-election bid. On Wednesday, she made no mention of impeachment in a statement vowing that “Congress will continue to investigate and legislate to protect our elections and secure our democracy.”

Representative Gerald Connolly, a Virginia Democrat who is chairman of the House Oversight subcommittee on government operations, said in an interview that Mueller’s latest comments add “a lot of intensity” to “that movement toward impeachment.”

“It doesn’t mean the majority is there, or wants to do it, but it gets harder by the day to ignore what is in front of you,” he said, while adding that House committee investigations that are already underway need to play out.

On the GOP side, Representative Doug Collins, the top Republican on the House Judiciary panel, said “it is time to move on.”

“Relitigating the 2016 election and reinvestigating the special counsel’s findings will only further divide our country,” he said in a statement.

Mueller’s report, with some redactions, was released by Barr on April 18 -- but only after he issued summaries that Democrats said were tilted to favor Trump. Barr said Mueller reached no conclusion on obstruction of justice by Trump so he and Deputy Attorney General Rod Rosenstein made their own finding that there wasn’t evidence to make a criminal case against the president. The summaries led to Trump’s frequent tweets that Mueller found “NO COLLUSION and NO OBSTRUCTION!”

Mueller complained about Barr’s summaries in a letter to the attorney general in March that later was made public.

“The summary letter the department sent to Congress and released to the public late in the afternoon of March 24 did not fully capture the context, nature, and substance of this office’s work and conclusions,” Mueller wrote. Barr dismissed the complaint as “a bit snitty” in testimony before the Senate Judiciary Committee.

While the special counsel’s probe has been closed, he had remained in his post as a Justice Department employee. His final report included notice that he referred 14 investigations to various U.S. attorneys, most of which still remain secret.

Republicans have their own set of questions, mostly related to the origins of the Russia probe that they say was tainted by anti-Trump bias among some FBI agents and Justice Department officials. Barr has opened his own review into the origins of the Russia investigation.

Mueller took the opportunity to defend his investigation in the face of the heightened attacks by Trump and his allies to discredit a probe that Trump regularly calls a partisan “witch hunt.” The special counsel said the efforts by Russia to interfere in the 2016 election deserved the Justice Department’s attention, were of “paramount importance” and “deserve the attention of every American.”

He also defended the investigation into whether Trump obstructed justice, saying "it was critical for us to obtain full and accurate information from every person we questioned. When a subject of an investigation obstructs that investigation or lies to investigators it strikes at the core of the government’s effort to find the truth and hold wrong doers accountable."

Trump has repeatedly accused Mueller’s staff of being "angry Democrats." Mueller rebutted that, too, calling his attorneys and investigators individuals of the "highest integrity."

Mueller’s investigation exposed a "sweeping and systematic" operation by the Russian government to interfere in the election, including making multiple contacts with officials associated with Trump’s presidential campaign. Barr released a redacted version of the report on April 18.

Although the investigation didn’t establish that members of the Trump campaign conspired or coordinated with the Russian government, Mueller "identified numerous links between the Russian government and the Trump campaign," according to his report.

 “The investigation established that the Russian government perceived it would benefit from a Trump presidency and worked to secure that outcome, and that the campaign expected it would benefit electorally from information stolen and released through Russian efforts," the report said.

Mueller also chronicled at least 10 instances in which Trump acted to obstruct the investigation, only to be stymied in some efforts by the refusal of his aides to carry out his orders.