WASHINGTON — One day before a mob of former President Donald J. Trump’s supporters stormed the Capitol, Stephen K. Bannon, a former top adviser to Mr. Trump, made a prediction to listeners of his radio show.
“Now we’re on, as they say, the point of attack — the point of attack tomorrow,” Mr. Bannon said on Jan. 5 as he promoted a plan hatched by Mr. Trump and far-right Republican lawmakers to try to overturn President Biden’s victory the next day, when Congress would meet to formalize the election results. “It’s going to kick off. It’s going to be very dramatic.”
It is because of comments like that, which foreshadowed the violence that played out during the Capitol riot, that the House committee investigating the assault is interested in questioning Mr. Bannon. But the former counselor to Mr. Trump has refused to cooperate with the inquiry, citing the former president’s claim of executive privilege.
The panel on Tuesday voted unanimously to recommend charging Mr. Bannon with criminal contempt of Congress for defying its subpoena, sending the matter to the House, which is expected to approve the move and hand the matter over to the Justice Department for prosecution.
“The rule of law remains under attack right now,” said Representative Bennie Thompson, Democrat of Mississippi and the chairman of the committee. “Mr. Bannon will comply with our investigation, or he will face the consequences.”
Mr. Thompson said he expected the full House to “quickly” take up the matter.
The high-profile confrontation is the first of several that promise to test the boundaries of executive privilege — the presidential prerogative to keep official communications secret — and will determine how far the House committee will be able to go in uncovering the story behind the deadliest attack on the Capitol in two centuries.
Mr. Trump has filed his own federal lawsuit that touches on similar questions, suing both the chairman of the investigative committee and the head of the National Archives, the custodian of his presidential records, to block the release of material the panel has requested.
Many Democrats fear that case, as well as any the Justice Department might decide to bring against Mr. Bannon, may drag on for months, potentially long enough for Republicans to gain the House majority in 2022 and bury the inquiry — and with it, any hope of revealing fresh information about what precipitated the riot.
Members of the committee, which is controlled by Democrats, believe that Mr. Bannon has crucial information about plans to undermine Mr. Biden’s victory, including conversations Mr. Bannon had with Mr. Trump in which he urged the former president to focus his efforts on Jan. 6.
In a report recommending the House find Mr. Bannon in contempt, the committee repeatedly cited comments he made on his radio show on Jan. 5 — when Mr. Bannon promised “all hell is going to break loose tomorrow” — as evidence that “he had some foreknowledge about extreme events that would occur the next day.”
Investigators wrote that Mr. Bannon appeared to “have had multiple roles relevant to this investigation,” including in constructing the “Stop the Steal” public relations effort to spread the lies of a fraudulent election that motivated the attack, and participating in events from a ‘‘war room” organized at a Washington, D.C., hotel with other allies of Mr. Trump who were seeking to overturn the election.
The group included members of the Trump campaign’s legal team, including Rudolph W. Giuliani and John C. Eastman; and prominent proponents of false election fraud claims, including Russell Ramsland Jr. and Boris Epshteyn; as well as Trump ally Roger J. Stone Jr., who left the hotel with members of the Oath Keepers militia group acting as bodyguards, the committee wrote.
“It’s not going to happen like you think it’s going to happen,” Mr. Bannon told his audience on Jan. 5. “It’s going to be extraordinarily different. And all I can say is: Strap in.”
Robert J. Costello, Mr. Bannon’s lawyer, has informed the committee that his client would not comply, citing Mr. Trump’s directive for his former aides and advisers facing subpoenas to invoke immunity and refrain from turning over documents that might be protected under executive privilege.
Late Monday, Mr. Bannon and his lawyer sought to delay the vote, citing Mr. Trump’s lawsuit seeking to block the disclosure of White House files related to his actions and communications surrounding the Jan. 6 Capitol riot. Mr. Thompson quickly denied the request for a delay.
Under federal law, any person summoned as a congressional witness who refuses to comply can face a misdemeanor charge that carries a fine of $100 to $100,000 and a jail sentence of one month to one year.
During the Tuesday committee meeting, Representative Liz Cheney, Republican of Wyoming and the committee’s vice chairwoman, directed a comment to her Republican colleagues, warning them that following Mr. Trump’s lies was a prescription for “national self-destruction.”
“Almost all of you know in your hearts that what happened on Jan. 6 was profoundly wrong,” she said. “You know that there is no evidence of widespread election fraud sufficient to overturn the election; you know that the Dominion voting machines were not corrupted by a foreign power. You know those claims are false.”
But both Mr. Bannon’s and Mr. Trump’s cases raise novel legal issues. The case against Mr. Bannon is untested because he has not been an executive branch official since he left the White House in 2017, and any conversations he may have had with Mr. Trump pertaining to Jan. 6 are likely to have fallen outside the former president’s official duties. No court has definitively said whether conversations with private citizens are covered by executive privilege, which is generally extended in relation to conversations or documents that pertain to presidential duties.
And the Biden administration has refused to assert executive privilege over any of Mr. Trump’s Jan. 6-related material, saying that it would not be in the public interest to keep secret the details of a plot to thwart the peaceful transfer of power.
Committee members said they were confident that they would prevail in their push to obtain the information.
“The former president’s clear objective is to stop the select committee from getting to the facts about Jan. 6, and his lawsuit is nothing more than an attempt to delay and obstruct our probe,” Mr. Thompson and Ms. Cheney wrote in response to Mr. Trump’s suit. “Precedent and law are on our side.”
Claims of executive privilege date back to the very first congressional investigation, in George Washington’s administration, said Douglas L. Kriner, a professor of government at Cornell University and author of the book “Investigating the President: Congressional Checks on Presidential Power.”
However, Mr. Bannon’s situation is different from many previous cases in which the privilege was invoked.
“It’s hard to imagine how this jeopardizes national security,” Mr. Kriner said of releasing documents from the Trump administration. “It doesn’t involve a current ongoing administration that might be harmed in any way, and it doesn’t even involve the right to frank and open conversation between the president and other advisers within the administration.”
The committee vote comes as some Senate Republicans are holding up the confirmation of Mr. Biden’s nominee for the U.S. Attorney in Washington, D.C., who would oversee charges against defendants related to the Jan. 6 attack, including any potential charges against Mr. Bannon.
Senator Mike Lee, Republican of Utah, has put a hold on the nomination of Matthew M. Graves to lead the office, according to two people with knowledge of the situation.
Representative Eleanor Holmes Norton, the District’s nonvoting delegate, said she was confident Mr. Graves would eventually win approval, but that his nomination had become mired in Republican hostility around the effort to investigate the Capitol riot.
“It really isn’t related to him at all,” Ms. Norton said. “It’s partisan. It does relate to Jan. 6. It’s a tantrum, really.”
Mr. Lee’s office did not respond to a request for comment.