Tuesday's hearing of the Select Committee to Investigate the January 6th Attack on the United States Capitol will focus on the role of the pro-Trump conspiracy theory known as QAnon, as well as the role of extremist groups like the Proud Boys and the Oath Keepers, aides to the committee said. A key area of inquiry for congressional investigators has been possible ties between former President Trump and his allies and far-right extremists. And aides said the committee would present new evidence about how Trump's tweet calling for a "big protest" on Jan. 6th served as a kind of call to arms. "Be there, will be wild!" Trump tweeted.

A former spokesperson for the Oath Keepers is slated to testify publicly as part of Tuesday's hearing. The spokesperson, Jason Van Tatenhove, told Colorado TV station KDVR he had served as the Oath Keepers' "propagandist" starting in 2014, but separated from the group several years before the attack on the Capitol.

Extremist groups have been at the forefront of the federal criminal investigation into the Capitol breach. Justice Department prosecutors have brought criminal charges against more than 130 people with apparent ties to extremist groups, including more than three dozen who appear to have expressed support for QAnon, according to NPR's database of charges. Leaders of both the Proud Boys and the Oath Keepers have been charged with seditious conspiracy, the most serious criminal charge stemming from the Jan. 6, 2021 attack. Three defendants have pleaded guilty to that charge, while other defendants are fighting the allegations.

Aides to the Jan. 6 select committee cited longtime Trump adviser Roger Stone and former National Security Adviser Michael Flynn as possible conduits between extremist groups and people in Trump's orbit. In 2020, both Stone and Flynn received presidential pardons from Trump. The two men had separately been convicted on charges connected to former Justice Department Special Counsel Robert Mueller's investigation into Russian interference in the 2016 presidential election.

Stone and Flynn have denied all wrongdoing related to the attack on the Capitol. In interviews with the committee, both asserted their Fifth Amendment right against self-incrimination.

Already-public information suggests ties between Stone, Flynn and extremists.

Stone, for example, has worked closely with Proud Boy leader Enrique Tarrio, and the two have appeared at events together. Tarrio was not in Washington, D.C. during the Capitol riot, but prosecutors have alleged that he conspired with members of the group to plan the attack. Tarrio has pleaded not guilty to the charges.

Members of the Oath Keepers also acted as part of a security detail for Stone on the morning of Jan. 6, prior to the riot. A week later, Stone said in an Instagram video that he was initially supposed to lead a march from the Ellipse to the Capitol that day, where he would give a speech, but he ultimately "decided that I was not interested in doing any of those things." He said he only supported peaceful protest that day, and "left town while demonstrators were still, to my astonishment, inside the Capitol."

Flynn has also received security help from the Oath Keepers, including at a pro-Trump event in Dec. 2020, according to the group's leader, Stewart Rhodes. At that event, Rhodes said Trump should "drop the hammer" and invoke the Insurrection Act, "because if he does not do it, we'll have to fight a bloody civil war or a bloody revolution to take our country back against a corrupt, illegitimate regime." Rhodes has also pleaded not guilty to charges of seditious conspiracy.

Thus far, the committee has not delved deeply into QAnon, which the Anti-Defamation League describes as a "remarkably elaborate conspiracy theory that has taken root within some parts of the pro-Trump movement," with "marked undertones of antisemitism and xenophobia."

During the 2020 presidential campaign, Trump declined to disavow QAnon or its supporters. "I don't know much about the movement, other than I understand they like me very much, which I appreciate," Trump said at an Aug. 2020 press conference. "I've heard these are people that love our country," Trump added.

Flynn also suggested support for QAnon. On July 4, 2020, he posted a video on Twitter, in which he and members of his family used the phrase "where we go one, we go all," a slogan closely associated with QAnon. (The slogan originally derives from the mid-1990s movie "White Squall.") Flynn's family has said the video was unrelated to QAnon, and was rather "a simple, family, July 4 statement of support for each other."

At a hearing last month, the select committee presented evidence suggesting that Stone and Flynn remained close to Trump's campaign to overturn the 2020 election results right up until the day of the riot.

"The night before January 6, President Trump instructed his chief of staff, Mark Meadows, to contact both Roger Stone and Michael Flynn regarding what would play out the next day," Rep. Liz Chenery (R-Wy.) said.

Former Trump White House aide Cassidy Hutchinson testified that Meadows made phone calls to both men, but she did not know what they discussed.

Hutchinson also testified that in the run-up to the riot, she heard conversations involving Trump adviser Rudy Giuliani.

"I recall hearing the word Oath Keeper and hearing the word Proud Boys closer to the planning of the January 6 rally when Mr. Giuliani would be around," Hutchinson testified.

The committee did not provide additional details about those discussions. Giuliani, through an attorney has denied links to either the Oath Keepers or the Proud Boys.

Jon Lewis, a research fellow at George Washington University's Program on Extremism, said congressional investigators have the difficult task of explaining the "confusing web" of linking Trump's allies and extremist groups.

"It's a small enough group of actors that everyone's only at any point going to be maybe two degrees of separation from Mark Meadows, to Giuliani to Enrique Tarrio, or someone like that," Lewis said.

Looking ahead to Tuesday's hearing, Lewis said he hopes the committee might provide more specific answers about "Who to talked to whom when, who witnessed that conversation, who can speak to what was actually communicated, and ultimately, what does that mean and why does that matter?"

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