The House committee investigating the Jan. 6 attack on the Capitol is expected to hear public testimony on Tuesday from Cassidy Hutchinson, a former aide to Mark Meadows, the final chief of staff for President Donald J. Trump, according to people familiar with the matter.
The committee on Monday abruptly scheduled a hearing for Tuesday afternoon to present what the panel called “recently obtained evidence.” But it did not disclose the nature of the evidence or say who would be testifying, touching off a wave of speculation.
The hearing is scheduled for 1 p.m. on Capitol Hill, according to a news release issued by the committee. Ms. Hutchinson’s planned testimony was reported earlier by Punchbowl News.
Ms. Hutchinson has provided the panel with some of its biggest revelations to date, all made during videotaped closed-door testimony, portions of which have been shown or alluded to in previous hearings.
She is said to have been present when Mr. Meadows described hearing Mr. Trump react approvingly to chants by his supporters to hang Vice President Mike Pence. And she testified that a half-dozen Republican lawmakers who led the efforts in Congress to overturn the election sought pardons after the riot.
It was not immediately clear what a short-notice hearing to hear from Ms. Hutchinson might reveal, given that she has already testified three times behind closed doors after receiving a subpoena and the committee has featured clips of her testimony in previous hearings.
The announcement — and its sudden and secretive nature — gave way to a day of guesswork about what the panel might have learned, or whose cooperation it may have secured, to warrant upending a carefully choreographed hearing schedule during a week when members had left Washington to spend time in their districts around the country.
“BETTER BE A BIG DEAL,” John W. Dean, the White House counsel under President Richard M. Nixon known for his role in the Watergate scandal, wrote on Twitter. “There was only one surprise witness during the Senate Watergate Committee hearings. On July 16, 1973 an unannounced witness appeared: Alex Butterfield, who testified to Nixon’s secret taping system — forever changing history!”
The Jan. 6 panel has held a series of hearings this month laying out the findings of its nearly yearlong investigation, but it had not been scheduled to have any additional sessions until July.
Still, its investigators have continued to gather evidence and record interviews with witnesses even as the committee presents its findings. At the end of each hearing, lawmakers have issued calls for more people to come forward and offer public testimony. And in recent days, the committee has indicated that it has gathered crucial new information that bears further exploration.
In recent days, the committee also obtained and has been poring over hours of footage shot by a documentary filmmaker who was embedded with Mr. Trump, his family and members of his inner circle immediately before, during and after the attack.
But pressed on the matter on Monday, aides declined to divulge what additional evidence they planned to present on Tuesday.
Some of the most damning testimony the panel has received so far has come from people who worked directly for Mr. Trump, including officials from his presidential campaign, his legal team and the Justice Department.
Ms. Hutchinson was asked by the committee about Mr. Trump’s positive reaction to the chants from rioters to execute Mr. Pence and confirmed it, according to people familiar with the panel’s work.
Representative Liz Cheney, Republican of Wyoming and the committee’s vice chairwoman, has said the committee received testimony that when Mr. Trump learned of the mob’s threats to hang Mr. Pence, he said, “Maybe our supporters have the right idea,” and added that Mr. Pence “deserves it.”
Ms. Hutchinson has also told the committee that Anthony M. Ornato, the former White House chief of operations, told Mr. Meadows that “we had intel reports saying that there could potentially be violence on the 6th,” and yet the White House did nothing to prevent the violence.
Ms. Hutchinson’s closed-door testimony also suggested that at least a handful of Republican lawmakers were concerned about criminal liability after participating in the effort to invalidate the election results. In a videotaped interview played by the panel at its last public hearing, Ms. Hutchinson testified that Representatives Mo Brooks of Alabama, Matt Gaetz of Florida, Louie Gohmert of Texas, Scott Perry of Pennsylvania, Andy Biggs of Arizona and Marjorie Taylor Greene of Georgia all sought pardons after the Jan. 6 assault.
Key Revelations From the Jan. 6 Hearings
Four of those members have denied doing so, with some questioning Ms. Hutchinson by name. Ms. Greene posted a clip of Ms. Hutchinson on Twitter and added: “Saying ‘I heard’ means you don’t know. Spreading gossip and lies is exactly what the Jan. 6 Witch Hunt Committee is all about.” Mr. Biggs similarly said that Ms. Hutchinson was “mistaken” and that her testimony was edited “deceptively.”
Mr. Brooks, however, confirmed seeking a broad pardon for more than 100 Republicans.
Ms. Hutchinson has also testified that in one discussion, Mr. Perry, who now leads the right-wing House Freedom Caucus, endorsed the idea of encouraging supporters to march to the Capitol, and that no one on the call objected to the proposal. She made clear that the members of Congress were “inclined to go with White House guidance” about directing a crowd to the Capitol.
The committee has also gathered testimony that Mr. Meadows used the fireplace in his office to burn documents, according to two people briefed on the panel’s questions. The committee has asked witnesses about how Mr. Meadows handled documents and records after the election.
The panel has yet to hear directly from Mr. Trump or Mr. Pence, though lawmakers have left open the possibility of calling either. The committee has also asked Virginia Thomas, the wife of Justice Clarence Thomas, to testify privately next month about her role in pushing for the 2020 election to be overturned.
Ms. Cheney has publicly called on Pat A. Cipollone, the former White House counsel who pushed back against some of the most extreme plans to overturn the election, to testify.
The committee had been planning at least two more hearings for July, according to its chairman, Representative Bennie Thompson, Democrat of Mississippi. Those sessions were expected to detail how a mob of violent extremists attacked the Capitol and how Mr. Trump did nothing to call off the violence for more than three hours.