Beginning on election night 2020 and continuing through his final days in office, Donald Trump unraveled and dragged America with him, to the point that his followers sacked the U.S. Capitol with two weeks left in his term. Axios takes you inside the collapse of a president with a special series.

Episode 4: Trump torches what is arguably the most consequential relationship in his Cabinet.

Attorney General Bill Barr stood behind a chair in the private dining room next to the Oval Office, looming over Donald Trump. The president sat at the head of the table. It was Dec. 1, nearly a month after the election, and Barr had some sharp advice to get off his chest. The president's theories about a stolen election, Barr told Trump, were "bullshit."

White House counsel Pat Cipollone and a few other aides in the room were shocked Barr had come out and said it — although they knew it was true. For good measure, the attorney general threw in a warning that the new legal team Trump was betting his future on was "clownish."

Trump had angrily dragged Barr in to explain himself after seeing a breaking AP story all over Twitter, with the headline: "Disputing Trump, Barr says no widespread election fraud." But Barr was not backing down. Three weeks later, he would be gone.

The relationship between the president and his attorney general was arguably the most consequential in Trump's Cabinet. And in the six months leading up to this meeting, the relationship between the two men had quietly disintegrated. Nobody was more loyal than Bill Barr. But for Trump, it was never enough.

The president had become too manic for even his most loyal allies, listening increasingly to the conspiracy theorists who echoed his own views and offered an illusion, an alternate reality.

By the late summer of 2020, Trump and Barr were regularly skirmishing over how to handle the rising Black Lives Matter protests sparked by the death of George Floyd while in police custody. As the national movement unfurled, some protests had given way to violence and looting. Trump wanted the U.S. government to crack down hard on the unrest.

The president wanted to invoke the Insurrection Act and send the military into U.S. cities. He wanted troops in the street. Some hardcore outside allies, including Judicial Watch president Tom Fitton, were egging him on. The thankless job of pushing back fell to Barr.

At times, Barr was the heat shield between the president and the chairman of the Joint Chiefs of Staff Mark Milley and Defense Secretary Mark Esper, both of whom strongly objected to Trump's fantasies of U.S. troops descending upon Portland.

The president regularly summoned a group of national security leaders to the Oval Office, and one mid-August meeting was particularly volatile.

From his seat behind the Resolute Desk, an agitated Trump told Barr to go and do something, and to do it right away — make an announcement, send in the troops, something. Just go in and resolve it, the president ordered. He wanted a devastating and provocative show of strength.

Barr disagreed. He thought the heat in the protests was gradually easing. He explained law enforcement strategy and his opinion that military intervention would backfire. Federal investigators were already hunting for the ringleaders in the protests.

Besides, Barr asked, what was the endgame for adding the military to the mix? Federal forces could end up stranded in a city like Portland indefinitely.

Trump grew more and more frustrated, but Barr pushed back harder, standing his ground in front of everyone in the room. He was ready, willing and able to be strong, he said. But, he added, we also have to be thoughtful.

What would these soldiers do, Barr pointed out. Just stand around and get yelled at? Trump didn't care. We look weak and this is hurting us, he ranted. Then he slammed his hand on the Resolute Desk.

"No one supports me," Trump yelled. "No one gives me any fucking support."

Trump got up and stormed out of the Oval Office to his private dining room, leaving Barr and the others behind. Barr glanced over at a red-faced White House chief of staff, Mark Meadows, and joked, "Well that went well."

Constant head-butting over how aggressive they should be was a serious irritant in the relationship. Trump wanted televised displays of shock and awe, particularly in Portland and Seattle.

Barr was no pacifist, but he thought Trump's ideas were more aggressive than necessary. They fought all summer, and Barr later privately compared the experience to "Groundhog Day." It was always Groundhog Day trying to explain things to Trump.

Trump was ricocheting between the advice of experienced advisers like Barr and Cipollone and the growing coterie of outside instigators like Fitton who were steadily gaining clout.

Publicly, Barr lauded Trump. Privately, his head hurt. By September, Barr was doing everything he could to avoid the president. There was little direct contact between the two men, and Barr had stopped visiting Trump at the White House.

He was sick of Trump making public statements and having others do so to whip up pressure against U.S. Attorney John Durham to bring more prosecutions or to put out a report on the Russia investigation before the election.

By mid-October, as Rudy Giuliani was trying to publicize the alleged contents of Hunter Biden's hard drive, Trump allies started pressuring Barr to appoint a special counsel to investigate his opponent's son. Unbeknownst to Trump, the Justice Department was already investigating Hunter Biden. But Barr, in keeping with department policy, had kept the investigation a secret.

Barr maneuvered so that he dealt primarily with Meadows and Cipollone. Those around the two men could see Barr was annoyed and frustrated by the president's constant needling.

Avoiding Trump became easier as the campaign heated up. The president spent more time on the trail and less time stewing in the Oval Office.

But Barr's respite ended after Election Day, as Trump teamed up with an array of conspiracy theorists to amplify preposterous theories of election interference, arguing that Biden and the Chinese Communist Party, among others, had stolen the election from him.

On Nov. 29, Trump told Fox News that Barr's Department of Justice was "missing in action." Barr was furious. In fact, the attorney general had jettisoned department precedent to speed up federal investigations of election fraud allegations. The Justice Department wasn't missing in action — there just wasn't any evidence of major fraud.

Barr gave an interview to the AP's beat reporter, Michael Balsamo, making this clear on the record. It would bring things to a head.

As he headed to the White House for meetings on Dec. 1, Barr knew Balsamo's story might go live while he was there. He soon found himself in the president's private dining room, along with Meadows, Cipollone, Trump and others. They sat at a long table under a glittering chandelier, amid Trump paraphernalia that was framed by floor-to-ceiling windows.

Trump was positioned in his usual seat at the head of the table, facing a huge flat-screen TV with the sound on low. On the screen, the conspiracy-drenched One America News network was playing a Michigan Senate hearing on election fraud.

Trump had seen Balsamo's story, and he was fuming. "Why would you say such a thing? You must hate Trump. There’s no other reason for it. You must hate Trump,” the president charged, speaking about himself in the third person.

"These things aren't panning out," Barr told the president, standing beside his chief of staff Will Levi. “The stuff that these people are filling your ear with just isn’t true.” Barr explained that if Trump wanted to contest the election results, the president's internal campaign lawyers would have to do it.

The Justice Department, he continued, had looked at the major fraud allegations that Trump's lawyers had leveled. "It's just bullshit," Barr told the president. Cipollone backed up Barr by saying the DOJ was investigating these claims.

Trump pointed at the TV and asked if Barr had been watching the hearing. Barr said he hadn't. "Maybe you should," the president said. Barr reiterated that the Justice Department was not ignoring the allegations, but that Trump's outside lawyers were doing a terrible job.

"I'm a pretty informed legal observer and I can't fucking figure out what the theory is here," he added. "It's just scattershot. It's all over the hill and gone."

"Maybe," Trump said. "Maybe."

A week later, the New York Times reported that Barr was considering resigning. Barr's relationship with the president was becoming untenable, and the president was listening to Sidney Powell and Giuliani instead of his White House counsel and attorney general.

Barr decided to quit before their private skirmishes spilled further into public view. Some speculated he had quit over the president's increasingly questionable pardons. But that had nothing to do with it. Barr had made it clear to Cipollone he did not want to be consulted on these post-election pardons. He did not need to hear about them until he received the official notices. The only pardon he made an effort to preemptively stop was for Edward Snowden.

On Dec. 14, Trump and Barr met one-on-one in the Oval Office. Others were there with Trump when the attorney general arrived. Barr asked for the room to be cleared so they could speak privately. He outlined his reasons for stepping aside early, explaining that while they'd had a good relationship, they now disagreed on key matters.

They did not need a public blowup. It was time to leave while the departure could still be amicable. Barr later told associates the meeting was calm and rational and that he'd written his resignation letter — which effusively praised the president for his policy achievements — the day before.

Trump appreciated Barr's loyalty and praise. But praise and loyalty were not enough.

On election fraud, Barr had told Trump what he did not want to hear and the president had stopped listening. It was time for Barr to go.

🎧 Listen to Jonathan Swan on Axios' new investigative podcast series, called "How it happened: Trump's last stand."

Read the rest of the "Off the rails" episodes here.

About this series: Our reporting is based on multiple interviews with current and former White House, campaign, government and congressional officials as well as direct eyewitnesses and people close to the president. Sources have been granted anonymity to share sensitive observations or details they would not be formally authorized to disclose. President Trump and other officials to whom quotes and actions have been attributed by others were provided the opportunity to confirm, deny or respond to reporting elements prior to publication.

"Off the rails" is reported by White House reporter Jonathan Swan, with reporting and research assistance by Zach Basu. It was edited by Margaret Talev and Mike Allen. Illustrations by Sarah Grillo, Aïda Amer and Eniola Odetunde.