WASHINGTON — Two days after Christmas last year, Richard P. Donoghue, a top Justice Department official in the waning days of the Trump administration, saw an unknown number appear on his phone.

Mr. Donoghue had spent weeks fielding calls, emails and in-person requests from President Donald J. Trump and his allies, all of whom asked the Justice Department to declare, falsely, that the election was corrupt. The lame-duck president had surrounded himself with a crew of unscrupulous lawyers, conspiracy theorists, even the chief executive of MyPillow — and they were stoking his election lies.

Mr. Trump had been handing out Mr. Donoghue’s cellphone number so that people could pass on rumors of election fraud. Who could be calling him now?

It turned out to be a member of Congress: Representative Scott Perry, Republican of Pennsylvania, who began pressing the president’s case. Mr. Perry said he had compiled a dossier of voter fraud allegations that the department needed to vet. Jeffrey Clark, a Justice Department lawyer who had found favor with Mr. Trump, could “do something” about the president’s claims, Mr. Perry said, even if others in the department would not.

The message was delivered by an obscure lawmaker who was doing Mr. Trump’s bidding. Justice Department officials viewed it as outrageous political pressure from a White House that had become consumed by conspiracy theories.

It was also one example of how a half-dozen right-wing members of Congress became key foot soldiers in Mr. Trump’s effort to overturn the election, according to dozens of interviews and a review of hundreds of pages of congressional testimony about the attack on the Capitol on Jan. 6.

The lawmakers — all of them members of the ultraconservative House Freedom Caucus — worked closely with the White House chief of staff, Mark Meadows, whose central role in Mr. Trump’s efforts to overturn a democratic election is coming into focus as the congressional investigation into Jan. 6 gains traction.

The men were not alone in their efforts — most Republican lawmakers fell in line behind Mr. Trump’s false claims of fraud, at least rhetorically — but this circle moved well beyond words and into action. They bombarded the Justice Department with dubious claims of voting irregularities. They pressured members of state legislatures to conduct audits that would cast doubt on the election results. They plotted to disrupt the certification on Jan. 6 of Joseph R. Biden Jr.’s victory.

There was Representative Jim Jordan of Ohio, the pugnacious former wrestler who bolstered his national profile by defending Mr. Trump on cable television; Representative Andy Biggs of Arizona, whose political ascent was padded by a $10 million sweepstakes win; and Representative Paul Gosar, an Arizona dentist who trafficked in conspiracy theories, spoke at a white nationalist rally and posted an animated video that depicted him killing Representative Alexandria Ocasio-Cortez, Democrat of New York.

They were joined by Representative Louie Gohmert of Texas, who was known for fiery speeches delivered to an empty House chamber and unsuccessfully sued Vice President Mike Pence over his refusal to interfere in the election certification; and Representative Mo Brooks of Alabama, a lawyer who rode the Tea Party wave to Congress and was later sued by a Democratic congressman for inciting the Jan. 6 riot.

Mr. Perry, a former Army helicopter pilot who is close to Mr. Jordan and Mr. Meadows, acted as a de facto sergeant. He coordinated many of the efforts to keep Mr. Trump in office, including a plan to replace the acting attorney general with a more compliant official. His colleagues call him General Perry.

Mr. Meadows, a former congressman from North Carolina who co-founded the Freedom Caucus in 2015, knew the six lawmakers well. His role as Mr. Trump’s right-hand man helped to remarkably empower the group in the president’s final, chaotic weeks in office.

In his book, “The Chief’s Chief,” Mr. Meadows insisted that he and Mr. Trump were simply trying to unfurl serious claims of election fraud. “All he wanted was time to get to the bottom of what really happened and get a fair count,” Mr. Meadows wrote.

Congressional Republicans have fought the Jan. 6 committee’s investigation at every turn, but it is increasingly clear that Mr. Trump relied on the lawmakers to help his attempts to retain power. When Justice Department officials said they could not find evidence of widespread fraud, Mr. Trump was unconcerned: “Just say that the election was corrupt + leave the rest to me and the R. Congressmen,” he said, according to Mr. Donoghue’s notes of the call.

November

On Nov. 9, two days after The Associated Press called the race for Mr. Biden, crisis meetings were underway at Trump campaign headquarters in Arlington, Va.

Mr. Perry and Mr. Jordan huddled with senior White House officials, including Mr. Meadows; Stephen Miller, a top Trump adviser; Bill Stepien, the campaign manager; and Kayleigh McEnany, the White House press secretary.

According to two people familiar with the meetings, which have not been previously reported, the group settled on a strategy that would become a blueprint for Mr. Trump’s supporters in Congress: Hammer home the idea that the election was tainted, announce legal actions being taken by the campaign, and bolster the case with allegations of fraud.

At a news conference later that day, Ms. McEnany delivered the message.

“This election is not over,” she said. “Far from it.”

On cable television and radio shows and at rallies, the lawmakers used unproved fraud claims to promote the idea that the election had been stolen. Mr. Brooks said he would never vote to certify Mr. Trump’s loss. Mr. Jordan told Fox News that ballots were counted in Pennsylvania after the election, contrary to state law. Mr. Gohmert claimed in Philadelphia that there was “rampant” voter fraud and later said on YouTube that the U.S. military had seized computer servers in Germany used to flip American votes.

Mr. Gosar pressed Doug Ducey, the Republican governor of Arizona, to investigate voting equipment made by Dominion Voting Systems, a company at the heart of several false conspiracy theories that Mr. Trump and his allies spread.

Mr. Gosar embraced the fraud claims so closely that his chief of staff, Tom Van Flein, rushed to an airplane hangar parking lot in Phoenix after a conspiracy theory began circulating that a suspicious jet carrying ballots from South Korea was about to land, perhaps in a bid to steal the election from Mr. Trump, according to court documents filed by one of the participants. The claim turned out to be baseless.

Mr. Van Flein did not respond to detailed questions about the episode.

Even as the fraud claims grew increasingly outlandish, Attorney General William P. Barr authorized federal prosecutors to look into “substantial allegations” of voting irregularities. Critics inside and outside the Justice Department slammed the move, saying it went against years of the department’s norms and chipped away at its credibility. But Mr. Barr privately told advisers that ignoring the allegations — no matter how implausible — would undermine faith in the election, according to Mr. Donoghue’s testimony.

And in any event, administration officials and lawmakers believed the claims would have little effect on the peaceful transfer of power to Mr. Biden from Mr. Trump, according to multiple former officials.

Mainstream Republicans like Senator Mitch McConnell of Kentucky, the majority leader, said on Nov. 9 that Mr. Trump had a right to investigate allegations of irregularities, “A few legal inquiries from the president do not exactly spell the end of the Republic,” Mr. McConnell said.

December

On Dec. 1, 2020, Mr. Barr said publicly what he knew to be true: The Justice Department had found no evidence of widespread election fraud. Mr. Biden was the lawful winner.

The attorney general’s declaration seemed only to energize the six lawmakers. Mr. Gohmert suggested that the F.B.I. in Washington could not be trusted to investigate election fraud. Mr. Biggs said that Mr. Trump’s allies needed “the imprimatur, quite frankly of the D.O.J.,” to win their lawsuits claiming fraud.

They turned their attention to Jan. 6, when Mr. Pence was to officially certify Mr. Biden’s victory. Mr. Jordan, asked if the president should concede, replied, “No way.”

The lawmakers started drumming up support to derail the transfer of power.

Mr. Gohmert sued Mr. Pence in an attempt to force him to nullify the results of the election. Mr. Perry circulated a letter written by Pennsylvania state legislators to Mr. McConnell and Representative Kevin McCarthy of California, the House Republican leader, asking Congress to delay certification. “I’m obliged to concur,” Mr. Perry wrote.

Mr. Meadows remained the key leader. When disputes broke out among organizers of the pro-Trump “Stop the Steal” rallies, he stepped in to mediate, according to two organizers, Dustin Stockton and Jennifer Lynn Lawrence.

In one case, Mr. Meadows helped settle a feud about whether to have one or two rallies on Jan. 6. The organizers decided that Mr. Trump would make what amounted to an opening statement about election fraud during his speech at the Ellipse, then the lawmakers would rise in succession during the congressional proceeding and present evidence they had gathered of purported fraud.

(That plan was ultimately derailed by the attack on Congress, Mr. Stockton said.)

On Dec. 21, Mr. Trump met with members of the Freedom Caucus to discuss their plans. Mr. Jordan, Mr. Gosar, Mr. Biggs, Mr. Brooks and Mr. Meadows were there.

“This sedition will be stopped,” Mr. Gosar wrote on Twitter.

Asked about the meeting, Mr. Gosar’s chief of staff said the congressman and his colleagues “have and had every right to attend rallies and speeches.”

“None of the members could have anticipated what occurred (on Jan. 6),” Mr. Van Flein added.

Mr. Perry was finding ways to exert pressure on the Justice Department. He introduced Mr. Trump to Mr. Clark, the acting head of the department’s civil division who became one of the Stop the Steal movement’s most ardent supporters.

Then, after Christmas, Mr. Perry called Mr. Donoghue to share his voter fraud dossier, which focused on unfounded election fraud claims in Pennsylvania.

“I had never heard of him before that day,” Mr. Donoghue would later testify to Senate investigators. He assumed that Mr. Trump had given Mr. Perry his personal cellphone number, as the president had done with others who were eager to pressure Justice Department officials to support the false idea of a rigged election.

Mr. Donoghue passed the dossier on to Scott Brady, the U.S. attorney for the Western District of Pennsylvania, with a note saying “for whatever it may be worth.”

Mr. Brady determined the allegations “were not well founded,” like so much of the flimsy evidence that the Trump campaign had dug up.

January

On Jan. 6, Washington was overcast and breezy as thousands of people gathered at the Ellipse to hear Mr. Trump and his allies spread a lie that has become a rallying cry in the months since: that the election was stolen from them in plain view.

Mr. Brooks, wearing body armor, took the stage in the morning, saying he was speaking at the behest of the White House. The crowd began to swell.

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

Just before noon, Mr. Pence released a letter that said he would not block certification. The power to choose the president, he said, belonged “to the American people, and to them alone.”

Mr. Trump approached the dais soon after and said the vice president did not have “the courage to do what should have been done to protect our country and our Constitution.”

“We will never give up,” Mr. Trump said. “We will never concede.”

Roaring their approval, many in the crowd began the walk down Pennsylvania Avenue toward the Capitol, where the certification proceeding was underway. Amped up by the speakers at the rally, the crowd taunted the officers who guarded the Capitol and pushed toward the building’s staircases and entry points, eventually breaching security along the perimeter just after 1 p.m.

By this point, the six lawmakers were inside the Capitol, ready to protest the certification. Mr. Gosar was speaking at 2:16 p.m. when security forces entered the chamber because rioters were in the building.

As the melee erupted, Senator Mitt Romney, Republican of Utah, yelled to his colleagues who were planning to challenge the election: “This is what you’ve gotten, guys.”

When Mr. Jordan tried to help Representative Liz Cheney, Republican of Wyoming, move to safety, she smacked his hand away, she later recounted to her aides.

“Get away from me,” she told him. “You fucking did this.”

A spokesman for Mr. Jordan disputed parts of the account, saying that Ms. Cheney did not curse at the congressman or slap him.

Of the six lawmakers, only Mr. Gosar and Mr. Jordan responded to requests for comment for this article, through their spokespeople.

The Aftermath

Mr. Perry was recently elected leader of the Freedom Caucus, elevating him to an influential leadership post as Republicans could regain control of the House in 2022. The stolen election claim is now a litmus test for the party, with Mr. Trump and his allies working to oust those who refuse to back it.

All six lawmakers are poised to be key supporters should Mr. Trump maintain his political clout before the midterm and general elections. Mr. Brooks is running for Senate in Alabama, and Mr. Gohmert is running for Texas attorney general.

Some, like Mr. Jordan, are in line to become committee chairs if Republicans take back the House. After Jan. 6, Mr. Jordan has claimed that he never said the election was stolen.

In many ways, they have tried to rewrite history. Several of the men have argued that the Jan. 6 attack was akin to a tourist visit to the Capitol. Mr. Gosar cast the attackers as “peaceful patriots across the country” who were harassed by federal prosecutors. A Pew research poll found that nearly two-thirds of Republicans said their party should not accept elected officials who criticize Mr. Trump.

Still, the House select committee investigating the Capitol attack appears to be picking up steam, voting this week to recommend that Mr. Meadows be charged with criminal contempt of Congress after he shifted from partly participating in the inquiry to waging a full-blown legal fight against the committee.

His fight is in line with Mr. Trump’s directive to stonewall the inquiry.

But the committee has signaled that it will investigate the role of members of Congress.

According to one prominent witness who was interviewed by the committee, investigators are interested in the relationship between Freedom Caucus members and political activists who organized “Stop the Steal” rallies before and after the election.

Representative Bennie Thompson, Democrat of Mississippi and the chairman of the committee, said the panel would follow the facts wherever they led, including to members of Congress.

“Nobody,” he said, “is off-limits.”