WASHINGTON — Standing before a crowd of thousands of MAGA-clad protesters on the National Mall on Wednesday, Representative Mo Brooks roared out a message that he said members of Congress who dared to accept President-elect Joseph R. Biden Jr.’s victory needed to hear.

“Today is the day American patriots start taking down names and kicking ass,” said Mr. Brooks, Republican of Alabama. “Are you willing to do what it takes to fight for America? Louder! Will you fight for America?”

Hours later, urged on by President Trump at the same rally, rioters stormed the Capitol, where Congress was meeting to formalize Mr. Biden’s election, chanting “Hang Mike Pence,” threatening to shoot Speaker Nancy Pelosi and forcing lawmakers to evacuate the building in a scene of violence and mayhem. Afterward, police officers recovered long guns, Molotov cocktails, explosive devices and zip ties. At least five people, including a Capitol Police officer, died during the protests and the siege and in the immediate aftermath.

Even after the tear gas cleared and the Capitol was secured, more than 135 House Republicans, including the party’s two top leaders, ultimately voted to throw out millions of lawfully cast votes, fulfilling the rioters’ demands and answering Mr. Trump’s call for Congress to subvert the election results in his favor.

But a handful of Mr. Trump’s most loyal allies in the House had gone even further in the days and weeks before the riot, urging their supporters to come to Washington on Jan. 6 to make a defiant last stand to keep him in power. They linked arms with the organizers of the protest and used inflammatory, bellicose language to describe the stakes.

Representatives Marjorie Taylor Greene of Georgia and Lauren Boebert of Colorado, first-term lawmakers who ran as outspoken defenders of Mr. Trump, referred to the day as Republicans’ “1776 moment.”

Representative Paul Gosar of Arizona, who for weeks promoted the Jan. 6 protest and other “Stop the Steal” events across the country more than a dozen times, repeatedly referred to Mr. Biden as an “illegitimate usurper” and suggested that Mr. Trump was the victim of an attempted “coup.”

“Be ready to defend the Constitution and the White House,” Mr. Gosar wrote in an op-ed titled “Are We Witnessing a Coup d’État?”

As rioters laid siege to the Capitol, Mr. Gosar posted a message of calm on Twitter, telling his followers, “Let’s not get carried away here.” But he wrote a far more sympathetic message on Parler, using the same photo of people scaling the walls of the building: “Americans are upset.”

Their comments have raised questions about the degree to which Republicans may have coordinated with protest organizers. In a since-deleted tweet, Representative Pete Sessions, Republican of Texas, wrote that he “had a great meeting today with the folks from Stop The Steal,” one of the leading groups that organized last week’s rally.

And in a separate video, Ali Alexander, a far-right activist and conspiracy theorist who emerged as a leader of Stop the Steal, claimed that he, along with Mr. Brooks, Mr. Gosar and Representative Andy Biggs of Arizona, had set the Jan. 6 event in motion.

“We four schemed up of putting maximum pressure on Congress while they were voting,” Mr. Alexander said in a since-deleted video, “so that who we couldn’t rally, we could change the hearts and the minds of Republicans who were in that body, hearing our loud roar from outside.”

A spokesman for Mr. Biggs denied in a statement on Monday that the lawmaker had had any role in organizing the rally, and said he had focused his efforts on working “within the confines of the law and established precedent to restore integrity to our elections.”

“Congressman Biggs is not aware of hearing of or meeting Mr. Alexander at any point — let alone working with him to organize some part of a planned protest on Jan. 6,” said the spokesman, Daniel Stefanski. “He did not have any contact with protesters or rioters, nor did he ever encourage or foster the rally or protests on Jan. 6.”

But Mr. Gosar appeared to be on friendly terms with Mr. Alexander, frequently tagging him in Twitter posts. At a rally late last month outside the Arizona State Capitol at which Mr. Gosar spoke, Mr. Alexander called the congressman “the spirit animal of this movement.”

“He’s helped out where he could,” Mr. Alexander said. “He’s offered to call donors. We actually had our first D.C. march because he called me and he said, ‘You need to go to the Supreme Court.’ I said, ‘All right, my captain.’ And that’s what started that.”

For his part, Mr. Brooks has remained unapologetic about his role in encouraging the rioters.

“I make no apology for doing my absolute best to inspire patriotic Americans to not give up on our country and to fight back against anti-Christian socialists in the 2022 and 2024 elections,” Mr. Brooks told a local newspaper. “I encourage EVERY citizen to watch my entire rally speech and decide for themselves what kind of America they want: One based on freedom and liberty or one based on godless dictatorial power.”

Representative Tom Malinowski, Democrat of New Jersey, on Monday introduced a resolution to formally censure Mr. Brooks, asserting that he was responsible for inciting the crowd and “endangering the lives of his fellow members of Congress.”

“We’re going to need to take a broader look at members of Congress who may have encouraged or even facilitated the attack on the Capitol,” Mr. Malinowski said in an interview.

“People like Brooks literally endangered the lives of their fellow members,” he said.

Other House Democrats were pushing to invoke Section 3 of the 14th Amendment, added after the Civil War, which disqualifies people who “have engaged in insurrection or rebellion” against the United States from holding public office. The clause was originally enacted to limit the influence of former Confederates in the Reconstruction era.

Representative Cori Bush, Democrat of Missouri, introduced a resolution on Monday with 47 co-sponsors that would initiate investigations for “removal of the members who attempted to overturn the results of the election and incited a white supremacist attempted coup.”

“I can’t act like it didn’t affect me,” Ms. Bush said in an interview of being in the Capitol during the siege. “I felt in danger. My staff was in danger.”

Ms. Bush said she did not know ultimately how many members of Congress should be expelled, but expected to learn the number from an investigation of the Ethics Committee.

“Even if it’s just a few, we have to make sure the message is clear that you cannot be a sitting Congress member and incite an insurrection and work to overturn an election,” she said.

For weeks before the rally, mimicking Mr. Trump’s tone, Republican operatives and lawmakers had used inflammatory language to describe the president’s effort to overturn Mr. Biden’s victory.

At a Turning Point USA event in December, Representative Madison Cawthorn of North Carolina encouraged attendees to “call your congressman and feel free — you can lightly threaten them.”

“Say: ‘If you don’t support election integrity, I’m coming after you. Madison Cawthorn’s coming after you. Everybody’s coming after you,’” Mr. Cawthorn said.

Some of Mr. Trump’s closest allies in Congress, including Mr. Brooks, Mr. Gosar, Mr. Biggs and Ms. Greene, met with him at the White House in December to discuss their drive to overturn the election results. Lawmakers present described the meeting as a fairly dry one, centered on how the process would play out on the House and Senate floors.

But Mr. Gosar cast the meeting to his followers as a call to action, pledging not to “accept disenfranchisement” of those who voted for Mr. Trump.

“This sedition,” he wrote, “will be stopped.”

Kevin Roose contributed reporting.