As he fired up a crowd of Trump supporters gathered at Arizona's state capitol last month, Rep. Paul Gosar falsely assured them that the election results could still be overturned. "Once we conquer the Hill," the six-term Republican declared to a wave of cheers, "Donald Trump is returned to being the president."

Two and a half weeks later, Gosar was repeating baseless claims about stolen ballots and rigged voting machines in a speech to Congress when he found himself interrupted by chaos on the House floor. Within minutes, lawmakers were being evacuated out of the chambers as rioters advanced through the heart of American democracy -- spurred by the same rhetoric Gosar and some of his fellow Republicans had espoused.

The first part of Gosar's prediction, at least, had come true: Capitol Hill had been conquered.

The insurrection last week that left five people dead, including a Capitol police officer, has spurred a new move to impeach President Donald Trump and a wave of criticism for the most prominent senators who voted to block President-elect Joe Biden's victory. But Gosar and several other of his GOP colleagues in the House are also facing new scrutiny for their incendiary language in the hours, days and weeks before the siege.

One of the top organizers of the movement that aimed to overturn the election results has claimed he worked closely with Republican congressmen. Ali Alexander, a leader of the "Stop the Steal" group, said in several Periscope livestream videos last month that he planned the rally that preceded the riot in conjunction with Gosar and two other congressional Republicans, Mo Brooks of Alabama and Andy Biggs of Arizona, as CNN first reported last week.

"We're the four guys who came up with a January 6 event," Alexander said in one video in December. "It was to build momentum and pressure and then on the day change hearts and minds of Congress peoples who weren't yet decided or saw everyone outside and said, 'I can't be on the other side of that mob.'"

Brooks, a staunch conservative and one of Trump's closest congressional allies, was one of the first speakers at the National Mall rally that preceded the riot, and his fiery language helped set the tone for what came next.

"Today is the day American patriots start taking down names and kicking ass!" the six-term Republican shouted to the assembled protesters. "Our ancestors sacrificed their blood, their sweat, their tears, their fortunes and sometimes their lives... Are you willing to do the same?"

Hours later, when some of the same people Brooks had spoken to were smashing windows at the US Capitol, the lawmaker livetweeted as he and his colleagues were being evacuated from the House chambers.

"Tear gas dispersed in Capitol Rotunda," Brooks wrote in a tweet posted from his iPad. "Congressmen ordered to grab gas masks under chairs in case have to leave in haste!"

Brooks was the first member of Congress to say publicly that he would object to the certification of the electoral votes for Biden. The day before the Jan. 6 rally, he tweeted that Trump had "asked me personally to speak & tell the American people about the election system weaknesses that the Socialist Democrats exploited to steal this election."

After the insurrection, while Brooks condemned rioters and called for them to be "prosecuted to the fullest extent of the law," he has also repeatedly suggested on social media and in interviews that at least some of the people who stormed the Capitol were members of the left-wing group Antifa -- a baseless claim that has been widely debunked.

Like Trump, who said Tuesday that his remarks at the rally, when he urged supporters to "fight like hell," were "totally appropriate," Brooks has denied responsibility for the riot, telling a radio show host the day after the attack that he "absolutely" had no regrets.

He later argued in a statement Tuesday that his remarks could not have been the cause of the violence. "No one at the rally interpreted my remarks to be anything other than what they were: A pep talk after the derriere kicking conservatives suffered in the dismal 2020 elections," Brooks wrote.

Gosar has closely associated himself with the Stop the Steal movement for months. He tagged or replied to Alexander in more than two dozen tweets since Election Day, sharing false rumors about mysteriously appearing ballots and deleted vote counts, and spoke at the December 19 rally at the Arizona state capitol that Alexander organized. He penned an online open letter last month titled "Are We Witnessing a Coup d'etat?"

"Biden should concede," Gosar tweeted on the morning of last week's congressional vote, sharing a photo of the pro-Trump protesters gathered in front of the Washington Monument. "I want his concession on my desk tomorrow morning. Don't make me come over there."

As the insurrection was still going on, Gosar shared divergent messages about the rioters. In one tweet with a photo of people scaling the walls of the Capitol, Gosar wrote "let's not get carried away here," adding that "if anyone on the ground reads this and is beyond the line come back." But on the right-wing social media network Parler, which has since gone offline, Gosar posted the same image with a different caption: "Americans are upset."

Even Gosar's family members say his language has gone too far. Several of his siblings -- who recorded a viral campaign ad for one of his opponents in 2018 -- have argued he should resign or be removed.

"My brother swore an oath to defend the Constitution against enemies foreign and domestic," the congressman's younger brother Tim Gosar, a private investigator in Fort Collins, Colorado, told CNN this week. "And he has blatantly broken that oath."

Gosar's office did not respond to a request for comment.

At the Arizona Stop the Steal rally with Gosar, Alexander played a video that he said Biggs, the chair of the conservative Freedom Caucus, had sent for the crowd.

"Andy Biggs here," the Arizona congressman said in the recording. "I wish I could be with you. I'm in the DC swamp fighting on behalf of Arizona's residents and freedom fighters all over the country." The crowd responded with a chant of "Biggs! Biggs! Biggs!" The Arizona Republic first reported the video on Monday.

A Biggs spokesperson told CNN that the congressman recorded the video at the request of Gosar's staff, and had never worked with Alexander.

"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," the spokesperson said. "He did not have any contact with protestors or rioters, nor did he ever encourage or foster the rally or protests."

Biggs was one of several Republican members of Congress who refused to wear masks in a secure room where lawmakers were staying during the riot, according to a video posted by the congressional news site Punchbowl. Several Democratic members have said in recent days that they tested positive for Covid after being in the room.

Other congressional Republicans also painted their efforts to oppose Biden's victory in sweeping, historic terms. In the days before the riot, Freshman Reps. Laura Boebert of Colorado and Marjorie Taylor Greene of Georgia both called the Wednesday electoral vote certification a "1776 moment."

And speaking at the same rally as Brooks and Trump, Rep. Madison Cawthorn of North Carolina, another newly elected member, told the crowd that "the Republicans are hiding and not fighting" and "they are trying to silence your voice."

"I want you to chant with me so loud that the cowards in Washington DC that I serve with can hear you," he declared.

A Cawthorn spokesperson said the congressman condemned the violence during the riot and has criticized Trump for "directing protestors toward the Capitol."

Two Democrats have introduced a resolution to censure Brooks for his comments at the rally, and others have argued for expelling Gosar and other congressional Republicans who backed efforts to overturn the election. Democratic leaders have not made plans yet to vote on a censure resolution, but the subject has been discussed repeatedly during private conference calls, Democratic sources say.

"Mo Brooks and others like him should resign," Rep. Jim McGovern, a Massachusetts Democrat, said on CNN Monday. "They should have the decency to resign. They don't belong in this institution. They have demonstrated a contempt for democracy and for freedom."

Denver Riggleman, a moderate Republican who lost his primary nomination last year to a more conservative challenger, said that he thought GOP leaders needed to have a "come to Jesus" moment and hold the congressmen who fanned the flames of insurrection accountable. But he said he doubted that the GOP base would punish members like Gosar or Brooks when they were back on the ballot.

"Those elected officials probably will get reelected, and that's that's the issue that we have right now," Riggleman said. "I think that's what scares me the most."

CNN's Nelli Black, Yahya Abou-Ghazala, Ben Naughton, Bob Ortega contributed to this report.