WASHINGTON - For months, the House committee investigating the Jan. 6, 2021, attack on the U.S. Capitol meticulously gathered evidence, carefully wrote and rewrote scripts, and painstakingly assembled video testimony to present at its televised hearings.

Then came Monday, when that pattern of extreme caution yielded to a scramble. With less than 24 hours' notice, the committee announced there would be a hearing the following afternoon with a single live witness: 25-year old Cassidy Hutchinson, a former junior White House aide.

The result was the most explosive day of testimony to date in a string of revelation-rich hearings. Hutchinson testified that former president Donald Trump knew his supporters were carrying weapons that day but urged them to the Capitol anyway. She also recounted deputy chief of staff Anthony Ornato telling her that Trump had lunged in rage at a Secret Service agent after the president was informed he could not accompany the rioters as they marched from the Ellipse.

Numerous people close to the committee's work say the abrupt decision to go public with Hutchinson's testimony, which surprised even some of its top aides and which involved presenting the world with details the committee itself had learned only days earlier, was necessary to prevent her account from leaking. With evidence that Trump allies were trying to influence her decision to talk, some members also worried she might back out if they waited any longer.

By rolling the dice, the committee attracted the attention it has sought for its message that Trump's role in precipitating the Jan. 6 attack was illegal, unconstitutional and disqualifying for any future bid for public office.

Hutchinson's account of cleaning Trump-strewn ketchup off White House walls and pleading with her onetime boss, former chief of staff Mark Meadows, to get off his phone and help quell the Capitol riot was watched by more viewers than all but one of the NBA Finals games this year.

But by rushing Hutchinson onto the witness stand, the committee has also exposed itself to criticism that it failed to thoroughly vet her claims.

Hutchinson has come under intense scrutiny from Trump and his allies, who have accused her of lying or derided her for relaying hearsay that would not hold up in a criminal proceeding.

So far, no one has publicly corroborated her account of a struggle between Trump and the Secret Service in his presidential SUV, but nor is anyone known to have disputed it under oath. Officials have said anonymously that the Secret Service agents involved are prepared to contradict Hutchinson in sworn testimony, although they do not appear to have done so.

One person familiar with the investigation who, like others, spoke on the condition of anonymity to address sensitive matters, called the story of Trump lunging at a Secret Service agent an "unforced error" that amounted to a colorful aside, when the main point, not in dispute, was that Trump was furious at being barred from proceeding to the Capitol.

"The reality is that Cassidy told the truth about a conversation that was relayed to her, and I can't see an incentive for her to lie about it," the person said. "But the reality is also that the committee has to be perfect. They probably shouldn't have brought it there. I think we know Secret Service agents get very protective of their details."

Others, however, supported the decision to move as expeditiously as possible in making Hutchinson's testimony public.

"It was exactly the right call," said Ted Boutrous, a prominent Democratic lawyer and donor. "They had a super-credible witness with no reason not to be telling the truth. There are reasons why she wouldn't have wanted to step forward. She relayed the facts very precisely as to what she was told."

Nick Akerman, a former federal prosecutor who investigated the Watergate scandal, noted that it is irrelevant that Hutchinson's testimony might not hold up in a criminal proceeding. The House committee is trying to persuade Americans that Trump should never again hold power, he said - and is doing so effectively by creating a dramatic, digestible storyline.

"She was very well-prepared," Akerman said. "And they minimized the risk by doing snippets on tape. You don't get to do this as a prosecutor, where you put your witness on and do your summation at the same time. The public is learning the full scope of what happened here."

A committee aide called Hutchinson's testimony "a landmark moment in the committee's work to uphold the rule of law and protect American democracy. Anyone who questions the gravity and impact of that hearing either didn't watch it, doesn't understand the committee's body of evidence, or has another agenda."

Public polling released in recent days offers little hint of whether the hearings have begun to change minds. A survey released Thursday by the Associated Press-NORC Center for Public Affairs Research at the University of Chicago shows that 49% of those surveyed say Trump bears responsibility for the Capitol attack, within the margin of error of the result in January, 46%.

Those numbers may not reflect the impact of Hutchinson's testimony on Tuesday, which drew the largest audiences of any of the daytime hearings so far. The committee's first hearing, which aired in prime time on June 9, drew more than 20 million viewers across a dozen outlets. Tuesday's Hutchinson hearing garnered 13 million viewers, according to Nielsen, a remarkable figure for daytime television.

Fox News, which did not air the prime time debut, has televised the panel's daytime work, and one of its most recognizable personalities has even praised it. "This testimony is stunning," Bret Baier, host of the network's 6 p.m. news show, said Tuesday during a break in Hutchinson's appearance.

Later, after the hearing concluded, Baier belittled Trump's attempts to deny her charges, noting that the former president was making his comments on his own social media platform and Hutchinson was "under oath on Capitol Hill."

The hearings have broken through with Trump voters in ways many inside-the-Beltway obsessions don't, according to Sarah Longwell, an anti-Trump Republican strategist who co-hosts the Bulwark's "Focus Group" podcast. In three groups conducted with Trump voters since the hearings began, participants reported being aware of the hearings or watching parts of them.

"This is not a technical term, but I would describe their engagement as 'hate-watching' some of it," Longwell said. "They say, 'Oh, I turned it off, it's so partisan, they're just trying to get Trump.' But at the end of the day, they're still following it."

Trump surrogates initially tried to dismiss the hearings and point to other subjects, such as gas prices. But that failed, Longwell said, because of how effectively the committee used Trump's own aides and other well-known Republicans as witnesses.

Trump's allies have been forced to respond, driving headlines and leading Fox News to dedicate coverage time to rebuttals. Trump has also been issuing a running commentary of the hearings on his Truth Social platform, marked by frequent denials.

"Her Fake story . . . is 'sick' and fraudulent," Trump wrote Tuesday of Hutchinson, calling the committee a "Kangaroo Court."

So far, however, the committee has avoided having to make any retractions, a possible reflection of the overall caution with which it has proceeded.

The panel twice announced delays because members said they needed to be careful not to make any mistakes in their preparation. On June 15, the third planned hearing was postponed to avoid holding three proceedings in a single week and risking errors.

"It's just technical issues. The staff putting together all the videos, you know, doing 1, 2, 3 - it was overwhelming," Rep. Zoe Lofgren, D-Calif., a committee member, told reporters that day in the Capitol. "So we're trying to give them a little room to get their work done."

A week later, as the rest of Congress headed toward a 17-day break, the committee dropped plans to hold one or more hearings during the Independence Day recess for similar reasons: An avalanche of new material needed to be carefully digested and reviewed before it could be put on display before a nationally televised audience.

Lawmakers and committee aides have described a process in which their teams scour depositions, both written and video, to collect the most revealing details and package them together. Then the team goes back into the depositions and video to see what the witnesses said just before and after the selected clips, to protect against any suggestion from Trump-friendly witnesses that they were quoted out of context.

By taking the time to check the details, committee members said they hoped to avoid giving Trump and his allies ammunition to discredit their work.

"There's been a deluge of new evidence since we got started. And we just need to catch our breath, go through the new evidence, and then incorporate it into the hearings we have planned," Rep. Jamie Raskin, D-Md., told reporters on June 22.

But Hutchinson's disclosures triggered a change of plans.

Hutchinson gave her first of four closed-door depositions to the committee in February. Some of the most compelling details from Tuesday's hearing, however, did not emerge until the last of those sessions, during the week of June 20. Afterward, committee members agreed that they needed to question Hutchinson at a live hearing as soon as possible.

If not, they feared the details would leak out, drip by drip, undermining the drama of a highly scripted televised hearing. Members also worried that pro-Trump forces would attempt, perhaps successfully, to intimidate Hutchinson into changing her story or refusing to testify in public.

The young woman's willingness to risk her career and subject herself to an onslaught of abuse from Trump supporters presented an additional potential benefit, according to several people with knowledge of the committee's deliberations: It would contrast sharply with the reluctance of several high-ranking Trump aides, notably former White House counsel Pat Cipollone, to come before the committee.

With Hutchinson's appearance, the committee was "absolutely" hoping to shame other witnesses into coming forward or saying more than they already have, one of the individuals said. Since Hutchinson's testimony, Cipollone has been subpoenaed and continues to correspond with the committee about potential testimony, multiple people confirmed.

Most members of the committee did not know exactly what Hutchinson planned to say until Tuesday morning, one individual with knowledge of the hearings said. Members were asked not to do any television or media before the hearing began, but were told it would be a big moment and to plan for a "robust TV schedule" afterward. The committee promised to connect members with television bookers to appear across the airwaves Tuesday afternoon.

"There will be no information outside of the fact that we are having a hearing tomorrow announced," a committee spokeswoman, told staffers on Monday. Later in an email, she reiterated: "We will not be giving out any information."

How Hutchinson's testimony influences the remainder of the committee's work is still unclear. Tentative plans to hold the committee's final two hearings the week of July 11 - including a prime time proceeding on July 14 focused primarily on Trump - are in flux, according to multiple members.

Much of Hutchinson's testimony Tuesday was originally planned to be featured in that final hearing, which must now be reworked. The committee is also hoping that, as more witnesses step forward, more information can be presented to the public.

To some close observers, the Hutchinson gamble has already paid off.

"For those that argue it was a mistake or an unforced error, we'll find out, but that ignores the committee's very capable march up until now," said Norm Eisen, who served as special counsel to the House Judiciary Committee during its first impeachment of Trump. "After all you've seen and perhaps the greatest congressional hearings ever - maybe surpassing Watergate - do you really think that they screwed it up? I sure don't think so."

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The Washington Post's Isaac Arnsdorf and Scott Clement contributed to this report.