Former special counsel Robert S. Mueller III, in quiet and occasionally halting testimony, warned Congress on Wednesday that Russia is still interfering with American democracy and offered some sharp criticism of President Trump.

“They’re doing it as we sit here, and they expect to do it in the next campaign,” Mueller said of the Russians, during roughly six hours of highly anticipated testimony before two House committees about his investigation of Russian election interference and Trump’s possible obstruction of justice.

Mueller’s appearance offered the prospect of pulling back the curtain on his secretive investigation, but the former prosecutor and FBI director strove — by day’s end successfully — not to reveal any details beyond his staff’s 448-page report.

Some Democrats had hoped his testimony would lead to a fresh groundswell of support to begin impeachment proceedings, but that seemed unlikely in the immediate aftermath of the hearings, which produced no blockbuster revelations. Mueller seemed reluctant to even utter the word “impeachment.”

Former special counsel Robert S. Mueller III said July 24 the Trump campaign's communication with WikiLeaks during the 2016 election was "disturbing." (The Washington Post)

Republicans pronounced the matter dead, and Trump declared victory.

“We had a very good day, the Republican Party,” the president told reporters at the White House. “There was no defense of what Robert Mueller was trying to defend . . . this ridiculous hoax, this witch hunt.”

He called Mueller’s performance “horrible.”

Mueller, who only hours earlier had specifically denied his investigation was a hoax or a witch hunt, appeared grim and determined in the packed hearing room but also at times confused or unable to hear the questions being asked — particularly in the morning, when the House Judiciary Committee questioned him about whether the president obstructed justice by attempting to impede Mueller’s work.

In the afternoon session, before the House Intelligence Committee, Mueller was much more forceful in describing the dangers posed by foreign attempts to sway U.S. elections.

“We have underplayed to a certain extent that aspect of our investigation,” Mueller said, adding that Russia’s multipronged effort to undermine the 2016 election could do “long-term damage to the United States that we need to move quickly to address.”

Mueller, 74, said his team’s report was meant to serve as “our living message to those who came after us” so that they “don’t let this problem continue to linger as it has over so many years.”

Asked about Trump campaign officials’ interactions with Russians who offered help to their election efforts, Mueller said he hoped future campaigns would not think it acceptable to receive assistance from foreign governments or to decide not to report such overtures to the FBI.

“I hope this is not the new normal, but I fear it is,” Mueller said.

He faulted Trump for praising the anti-secrecy group WikiLeaks, which U.S. officials have said acts like a “hostile intelligence service” and which was a conduit for Democratic Party files hacked by the Russians.

Rep. Mike Quigley (D-Ill.) read to the former special counsel a series of statements made by Trump when he was a candidate, including his declaration, “I love WikiLeaks.” Quigley then asked whether Mueller found those remarks disturbing.

“Problematic is an understatement in terms of what it displays of giving some hope or some boost to what is and should be illegal behavior,” Mueller said.

Mueller explained a critical decision that has long concerned Democrats – why the special counsel decided not to subpoena the president. Trump’s lawyers offered written answers to the special counsel’s office, which viewed those responses as incomplete.

After about a year of negotiating for an interview with the president, Mueller said, he and his team determined it was not worth a prolonged legal battle because they expected Trump would challenge any subpoena in the courts.

“The reason we didn’t do the interview was because of the length of time that it would take to resolve the issues attendant to that,” Mueller said.

For two years, Mueller’s work had proceeded under a shroud of secrecy and provoked endless speculation about its course. With the first few words of his testimony, Mueller sought to tamp down expectations that his testimony would go beyond his report.

“I do not intend to summarize or describe the results of our work in a different way,” he said.

As lawmakers peppered him with questions, Mueller often replied with variations of “I will refer you to the report,” or “I’m not going to get into that.”

Some of Mueller’s most impassioned testimony came in defense of his staff in the special counsel’s office. Trump and his supporters have attacked the prosecutors on the case as angry Democrats hellbent on bringing down the president.

“I’ve been in this business for almost 25 years. In those 25 years, I’ve not had occasion once to ask about somebody’s political affiliation,” Mueller said. “It is not done. What I care about is the capability of the individual to do the job and do the job seriously and quickly and with integrity.”

Mueller later added: “It is not a witch hunt.”

He frequently asked lawmakers to repeat their questions, saying that he could not hear them or that they were speaking too fast. He also said he was unfamiliar with some of the specifics of the investigation — a surprising admission for a prosecutor who built a distinguished career on delving deep into the weeds of investigations, to the point that many of his subordinates complained he was a maddening micromanager

He called the president “Trimp” before quickly correcting himself. He said he was “not familiar” with the opposition research firm Fusion GPS that commissioned a dossier of allegations that played a key role in the early days of the investigation into Russian interference, before Mueller was appointed as special counsel in May 2017. At another point, he could not recall the word “conspiracy” — a basic staple in any federal prosecutor’s lexicon — and a lawmaker supplied it for him. In the hearing room, Mueller’s muffled voice made his minimal responses nearly inaudible, a sharp contrast to the lawmakers, whose voices often boomed with indignation.

David Axelrod, a former adviser to President Barack Obama, tweeted: “This is delicate to say, but Mueller, whom I deeply respect, has not publicly testified before Congress in at least six years. And he does not appear as sharp as he was then.”

Before the hearing, current and former law enforcement officials who have worked with Mueller expressed concerns that he was stepping into a high-octane hearing that would be a tough test of his public demeanor — typically understated and technical.

Part of Mueller’s approach appeared strategic — with so many sensitive investigative areas that he was unwilling to talk about, the less he engaged on those subjects, the more easily his time at the witness table might pass.

When Republicans charged that the gen­esis of the Russia investigation was hopelessly tainted by anti-Trump bias among some of the investigators, Mueller declined to discuss the issue, saying those matters are under review by the Justice Department inspector general and therefore beyond his purview.

Even friendly exchanges could cause Mueller to stumble. When Rep. Greg Stanton (D-Ariz.) asked which president nominated Mueller to serve as the top federal prosecutor in Massachusetts, Mueller guessed George H.W. Bush. In fact, it was Ronald Reagan.

Republicans quickly seized on the misstep. Matt Schlapp, a key Trump ally, tweeted: “Devastating Mueller can’t remember that Reagan picked him to be a USA from Massachusetts.” As the morning session wore on, Republicans outside the hearing room repeatedly suggested Mueller’s answers showed a poor command of the cases he oversaw.

A person familiar with the work of the special counsel conceded that while some of Mueller’s responses “might have been more crisp and expansive, his performance has no bearing on the reliability and integrity of the investigation.”

“Mueller was the team leader and responsible for virtually every facet of the investigation,” said the person, who spoke on the condition of anonymity because they were not authorized to talk publicly. This person said Mueller “has a full command of those facts, and to suggest otherwise is just plain wrong.”

Democrats said many of Mueller’s statements were damaging to the president and merited further investigation by Congress.

Intelligence Committee Chairman Adam B. Schiff (D-Calif.) ended Mueller’s long day of testimony by asking whether knowingly accepting foreign assistance is an unethical thing to do.

Mueller agreed, adding, “And a crime, given certain circumstances.”

“It’s also unpatriotic,” said Schiff. “True,” Mueller answered.

Democrats also sought to get Mueller to refute claims made by Trump about his findings.

“The president was not exculpated for the acts that he allegedly committed,” the former special counsel said early in the hearing.

“Did you actually totally exonerate the president?” asked Rep. Jerrold Nadler (D-N.Y.), chairman of the Judiciary Committee.

“No,” Mueller replied.

Asked whether the president, under Justice Department policy, could be prosecuted for obstruction of justice after he leaves office, Mueller responded: “True.”

Republicans accused Mueller of being unfair to the president and ignoring the traditional presumption of innocence.

Rep. John Ratcliffe (R-Tex.), noting that Mueller’s report said it could not exonerate the president, said it was a prosecutor’s job to charge or not charge someone — not make a statement about exoneration.

“This is a unique situation,” said Mueller, who pointed repeatedly to the long-standing Justice Department policy that a sitting president cannot be indicted. Mueller’s team concluded that the policy also prohibits the Justice Department from saying whether a sitting president committed a crime.

Ratcliffe replied that the presumption of innocence “exists for everyone. Everyone is entitled to it — including the president.”

He noted that Democrats have said Trump is not above the law.

“He’s not,” Ratcliffe said. “But he damn sure shouldn’t be below the law, which is where Volume II of this report puts him.”

Rachael Bade, Carol D. Leonnig, Shane Harris, Tom Hamburger, Robert Costa, John Wagner and Felicia Sonmez contributed to this report.