They've interviewed more than 300 witnesses, collected tens of thousands of documents and traveled around the country to talk to election officials who were pressured by Donald Trump.
Now, after six months of intense work, the House committee investigating the Jan. 6 insurrection is preparing to go public.
Related video above: Pelosi: 'Never forgive' Trump, lackeys for Jan. 6
In the coming months, members of the panel will start to reveal their findings against the backdrop of the former president and his allies' persistent efforts to whitewash the riots and reject suggestions that he helped instigate them. The committee also faces the burden of trying to persuade the American public that their conclusions are fact-based and credible.
But the nine lawmakers — seven Democrats and two Republicans — are united in their commitment to tell the full story of Jan. 6, and they are planning televised hearings and reports that will bring their findings out into the open.
Their goal is not only to show the severity of the riot but also to make a clear connection between the attack and Trump's brazen pressure on the states and Congress to overturn Joe Biden's legitimate election as president.
"The full picture is coming to light, despite President Trump's ongoing efforts to hide the picture," said Wyoming Rep. Liz Cheney, the committee's vice chairwoman and one of its two Republican members.
"I don't think there's any area of this broader history in which we aren't learning new things," she said.
While the fundamental facts of Jan. 6 are known, the committee says the extraordinary trove of material they have collected — 35,000 pages of records so far, including texts, emails and phone records from people close to Trump — is fleshing out critical details of the worst attack on the Capitol in two centuries, which played out on live television.
They hope to fill in the blanks about the preparations before the attack, the financing behind the Jan. 6 rally that preceded it and the extensive White House campaign to overturn the 2020 election. They are also investigating what Trump himself was doing as his supporters fought their way into the Capitol.
True accountability may be fleeting. Congressional investigations are not criminal cases and lawmakers cannot dole out punishments. Even as the committee works, Trump and his allies continue to push lies about election fraud while working to place similarly minded officials at all levels of state and local government.
"I think that the challenge that we face is that the attacks on our democracy are continuing — they didn't come to an end on Jan. 6," said another panel member, Rep. Adam Schiff, D-Calif., also chairman of the House Intelligence Committee.
Still, the lawmakers hope they can present the public with a thorough accounting that captures what could have been "an even more serious and deeper constitutional crisis," as Cheney put it.
"I think this is one of the single most important congressional investigations in history," Cheney said.
The committee is up against the clock. Republicans could disband the investigation if they win the House majority in the November 2022 elections. The committee's final report is expected before then, with a possible interim report coming in the spring or summer.
In the hearings, which could start in the coming weeks, the committee wants to "bring the people who conducted the elections to Washington and tell their story," said the panel's chairman, Rep. Bennie Thompson, D-Miss. Their testimony, he said, will further debunk Trump's claims of election fraud.
The committee has interviewed several election officials in battleground states, including Arizona, Georgia, Michigan and Pennsylvania, about Trump's pressure campaign. In some cases, staff have traveled to those states to gather more information.
The panel also is focusing on the preparations for the Jan. 6 rally near the White House where Trump told his supporters to "fight like hell" — and how the rioters may have planned to block the electoral count if they had been able to get their hands on the electoral ballots.
They need to amplify to the public, Thompson said, "that it was an organized effort to change the outcome of the election by bringing people to Washington ... and ultimately if all else failed, weaponize the people who came by sending them to the Capitol."
About 90% of the witnesses called by the committee have cooperated, Thompson said, despite the defiance of high-profile Trump allies such as Steve Bannon and former White House chief of staff Mark Meadows. Lawmakers said they have been effective at gathering information from other sources in part because they share a unity of purpose rarely seen in a congressional investigation.
House Republican leader Kevin McCarthy of California, a close Trump ally, decided not to appoint any GOP members to the committee after House Speaker Nancy Pelosi, D-Calif., rejected two of his picks last summer.
Pelosi, who created the select committee after Republican senators rejected an evenly bipartisan outside commission, subsequently appointed Republicans Cheney and Adam Kinzinger of Illinois, Trump critics who shared the Democrats' desire to investigate the attack.
"I think you can see that Kevin made an epic mistake," Kinzinger said. "I think part of the reason we've gone so fast and have been so effective so far is because we've decided and we have the ability to do this as a nonpartisan investigation."
Kinzinger said the investigation would be "a very different scene" if Republicans allied with Trump were participating and able to obstruct some of their work.
"I think in five or 10 years, when school kids learn about Jan. 6, they're going to get the accurate story," Kinzinger said. "And I think that's going to be dependent on what we do here."
Democrats say having two Republicans working with them has been an asset, especially as they try to reach conservative audiences who may still believe Trump's falsehoods about a stolen election.
"They bring to the table perspectives and ability to translate a little bit what is being reflected in conservative media, or how this might be viewed through a conservative lens," says Rep. Stephanie Murphy, D-Fla. "And that's been really helpful."
There is "no division, no hostility, no partisan bickering — it's like, let's just get this job done," said California Rep. Zoe Lofgren, another member and a veteran of congressional investigations going back to the Watergate investigation of President Richard Nixon when she was a staffer on the House Judiciary Committee.
The nine-member group has bonded over a friendly text chain where they discuss business and occasionally their personal lives. There are messages wishing a happy birthday, for example, or congratulating another on a child's wedding.
"It's good, it's how Congress should be," said Rep. Pete Aguilar, D-Calif.
Aguilar says the biggest challenges for the committee are the calendar and the small group of Trump loyalists who are trying to run out the clock by stonewalling or suing them. In the end, he said, he thinks the committee's final report will stand the test of time, similar to the investigations of the 9/11 attacks and Watergate.
For now, though, "we are still in the eye of the hurricane," Aguilar said.