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 8: The siege. An inside account of the deadly insurrection at the Capitol on Jan. 6 that ultimately failed to block the certification of the Electoral College. And, finally, Trump's concession.

On Jan. 6, White House deputy national security adviser Matt Pottinger entered the West Wing in the mid-afternoon, shortly after his colleagues' phones had lit up with an emergency curfew alert from D.C. Mayor Muriel Bowser.

Pottinger had been in meetings off-site — and unplugged — as President Trump began exhorting the huge throngs of his supporters gathered on the Ellipse to protest Congress certifying Joe Biden's win.

As he entered a suite that housed National Security Council staff, Pottinger saw his colleagues' mouths agape, eyes glued to the TV images of rioting at the Capitol. He snapped to attention: "What the fuck is going on?"

On the Senate floor, Sen. James Lankford was less than three minutes into explaining why he was objecting to Arizona's electoral votes when Chuck Grassley, president pro tempore of the Senate, slammed down his gavel and croaked from the head of the dais, "The Senate will stand in recess until the call of the chair."

Lankford, looking puzzled but calm, glanced up as the Republican floor assistant Tony Hanagan walked briskly to his side and murmured: "The protesters are in the building."

After goading his crowd like a ringmaster, Trump had climbed back into his motorcade for the short trip back to the White House — about 1,300 feet from the stand to the South Lawn as the crow flies — and retreated behind the gates.

Trump had lied to the crowd of frenzied supporters when he told them the vice president had the power to overturn the results of the U.S. presidential election. He had lied, too, when he said he would join them on their march up Pennsylvania Avenue to Congress to "show strength."

Safe back in the comfort of his private dining room, the president watched televised images of mobs of his backers charging the Capitol, some swarming the corridors in painted faces and feral outfits that looked like the end of the world. At first, he liked what he saw.

But elsewhere in the West Wing, his aides were assessing the scale of the catastrophe. Staff whispered that an increasingly erratic Trump was destroying his legacy and the Republican Party. Many had been uneasy since Trump began his campaign to overturn democracy and seize a second term from the jaws of defeat.

Fending off any unlawful orders had been the focus of some aides for the past month, along with wrapping up the administration's work with minimal damage — and staying out of meetings with Trump that could later require them to hire an expensive lawyer.

No one on Trump's senior team believed he was a risk to fire off a nuclear weapon, as House Speaker Nancy Pelosi had suggested. But it was impossible to talk to the president about anything other than his delusion of staying in office.

The job of getting his signoff on important policy items fell more and more to the worn-down chief of staff Mark Meadows, who'd lost weight and whose eyes lately were rimmed in red.

Jared Kushner was missing in action, having effectively checked out after his father-in-law placed Rudy Giuliani in charge of the campaign's legal efforts. Kushner was spending much of his time on trips abroad, hoping to cut 11th-hour deals.

Pottinger, a former journalist who had been instrumental in shaping the administration's hard-line approach to China, had warned National Security Adviser Robert O'Brien over the summer that he intended to leave on Election Day.

But as Nov. 3 loomed, O'Brien convinced Pottinger to stay on for the transition, whichever way the election went. Trump had been laying the groundwork to undermine the integrity of the election for months, and Pottinger feared foreign adversaries would exploit such a combustible situation.

The assailants instead had come from within.

In the West Wing, one of Pottinger's staff showed him a tweet that Trump had posted at 2:24 p.m. on Jan. 6, while the Capitol was under siege. It read: "Mike Pence didn't have the courage to do what should have been done to protect our Country and our Constitution." Trump was winding things up, not down.

Pottinger walked over to his desk and began packing up the rest of his belongings: a bottle of Tums, a few books, letters from staff and his world map. He was done. He would work through the night at the White House to get through the paperwork to finalize his resignation.

He called O'Brien and told him he was resigning forthwith. He urged his boss to stay on, and the two men discussed how to keep Pottinger's departure from triggering a wholesale collapse of the NSC.

O'Brien was in a secure facility at U.S. Southern Command in Florida while the storming of the Capitol was taking place. He had been meeting with Admiral Craig Faller, the SOUTHCOM commander who briefed him on efforts to push back on China's encroachments in Latin America and the Caribbean, as well as regional COVID-19 and counternarcotics efforts.

They also discussed transitioning these efforts to the Biden administration. There were no phones or TVs blaring in the secure facility. O'Brien was unaware of what was unfolding at the Capitol.

During the riots, a member of O'Brien's National Security Council staff entered the secure facility and passed him a note telling him he needed to get in touch with the vice president. O'Brien called Pence, who by then had been evacuated from the chamber into a secure room in the Capitol.

O'Brien immediately put out a series of tweets on his personal account in support of the vice president and condemning the riots. He arranged for the official NSC account to do the same. O'Brien had planned to spend time with the Coast Guard that afternoon. Instead, he cancelled those plans to rush back to Washington.

In the halls of the Capitol, chaos ruled. Just before Lankford learned of the protesters' presence, another senator's body man had come sprinting down one of the hallways outside the chamber, motioning wildly at a group of staffers: Run.

Suddenly, U.S. Capitol Police officers began funneling dozens of staff into the chamber. Sen. Mitt Romney glanced up, terror flashing across his face. The chamber was sealed.

Pence and members of the leadership had been whisked out while the rest of the senators remained in their seats. Staffers lined the chamber wall. When it came their time to evacuate, many left personal belongings — and even some cellphones — behind.

One of the parliamentarians, Leigh Hildebrand, knew to grab the mahogany boxes containing the Electoral College votes. This was precious cargo, and it was crucial to keep the historic paperwork out of marauders' hands.

Wedged into a single-file line, the unwieldy group moved from the Senate chambers down a narrow stairwell. Police and heavily armed agents blocked off doors and hallways. Some of the younger staffers cried.

As the line stalled, Sen. Lindsey Graham wandered over to a set of large windows overlooking a courtyard. A parade of blue Trump flags floated by. "Lindsey!" another senator snapped. "Get away from the window."

Below, police officers tried to jam a set of elevator doors with floor mats, small tables, and anything else they could get their hands on, to take the elevators offline and pen in the rioters on other floors of the Capitol. The group reached a deserted subway corridor, and a police officer came sprinting down the tracks, parting the crowd like the Red Sea.

The senators resumed their exodus, and someone cracked a poor joke about not being able to socially distance. An injured police officer emerged, leaning on another officer. Her eyes were red and swollen, possibly from chemical irritation, and she was clearly in pain.

At last the senators and their staffs reached their destination — a large hearing room with rows of long tables covered in black cloth.

Senate Sergeant-at-Arms Michael Stenger grabbed a microphone to give an update. He looked pale and shocked. He tried to speak, but his voice kept breaking. He tapped the microphone several times and cleared his throat but the words wouldn't come out.

Graham lost it. "This is ridiculous!" he shouted. "You all need to use every resource and every weapon to take back the Senate. Get these thugs out of here!"

"Shut up!" Sen. Sherrod Brown shot back, from behind the dais. "Shut up, let him speak!" A police officer took over, as Stenger retreated.

About 10 minutes later, Sen. Tim Scott stepped onto the dais and asked Barry Black, the 72-year-old chaplain of the Senate, to lead the room in prayer.

More than 90 senators, 40 staffers and dozens of Capitol Police officers bowed their heads.

Around 3:30 p.m., a short, stocky police officer with a gray crew cut and a smear of dried blood on the left side of his face stepped up to the dais with an update. Yes, the Capitol had been breached, he told them. But outside, scores of heavily armed federal agents in military gear were standing guard. They were in a secure location now. Officers would work to get people out on buses.

Meantime, staff brought in drinks from the vending machines and hot trays of beef, mashed potatoes and Brussels sprouts. When cellphone batteries ran low, senators formed a line for the ultrafast iPhone charger cable belonging to a member of Sen. Kelly Loeffler's staff.

Senators split off into their cliques to wait. A group of the Republicans who opposed the Electoral College certification huddled together, discussing what to do.

Four televisions were on, all set to CNN. The first image to flash across the screen showed a rioter in black tactical gear hanging by one hand onto a Senate balcony. Host Jake Tapper was excoriating Trump for inciting the siege, and Sens. Ted Cruz and Josh Hawley for leading challenges to Biden’s Electoral College victory.

Cruz and Hawley sat in the same back corner of the room. Several of their colleagues came over to work them. Cruz had already made his objection to Arizona's certification; Hawley's plan to object to Pennsylvania was the only thing standing in the way of sending the Senate home early. But Hawley intended to go ahead with it.

Sen. Amy Klobuchar stood up at one point and demanded that the Senate find a way to continue its business of counting the electoral votes. The room largely agreed. Momentum for resuming business grew to the point that staff began setting up microphones at each table.

But then President-elect Biden materialized on the TV to address the nation. The room fell silent. Sen. Tom Carper, who represented Biden's home state of Delaware and had served alongside Biden in the Senate for eight years, filmed the speech on his iPhone.

"At this hour, our democracy is under unprecedented assault," Biden said in a somber voice. "Unlike anything we’ve seen in modern times. An assault on the citadel of liberty." Biden urged Trump to step out on national television immediately and call for an end to the riot. At the end of his speech, the room erupted in bipartisan applause.

Moments later, CNN aired a recorded video message from Trump, speaking from the Rose Garden. "I know your pain, I know you're hurt. We had an election that was stolen from us, a landslide election," the president opened provocatively, before meekly telling his supporters they had to "go home."

But he ended defiantly, jaw up, telling his followers who brought mob rule to the Capitol, "We love you. You're very special." The president had done the minimum — less, really — and he had kept the mob on his hook.

Senate staff inside the room were steaming. "That was pathetic," one said angrily. The president couldn't even be bothered to make a live speech, and then essentially he had closed with a validation of the mob.

Within hours, major social media platforms had removed the president's video and suspended Trump's accounts, warning of the risks of further incitement.

Late into one of the more disgraceful days in American history, the House and Senate regrouped, determined to send a clear signal that they would not hand over the republic to rioters — or to Trump.

Democrats and enough Republicans came together to do what the law had required them to do all along. They certified Biden's win. Even hardcore Trump loyalists like Loeffler and Tennessee Senators Marsha Blackburn and Bill Hagerty, who had publicly promised to object to the certification, backed out after seeing the mob charge the Capitol.

Senate Majority Leader Mitch McConnell seethed. The events of Jan. 6 had foreclosed any possibility of him ever repairing his relationship with Trump.

In the weeks immediately following the election, McConnell had found Trump impossible to deal with, given his singular obsession with overturning his loss. Their interactions had essentially dried up by Thanksgiving.

The last conversation between the two men was on Dec. 15, when Trump called McConnell to tell him he had made a mistake by recognizing Biden as president-elect in a speech on the Senate floor. Earlier that morning, McConnell had called Meadows, Trump's chief of staff, to give him a heads up about what he was about to do.

As always, crossing Trump would have its costs. The president commenced a campaign of revenge, attacking McConnell publicly, threatening to shut down the government, vetoing the annual defense spending bill — and, in the eyes of party leaders, costing the GOP the Senate.

With the riots holding the senators in late on Jan. 6, McConnell didn't get home from the Capitol until around 4 o'clock the next morning. His wife, Transportation Secretary Elaine Chao, who was equally outraged, had been grappling with whether to submit her resignation right away after the mob — inspired by her boss and the nation's president — stormed the Capitol.

But Chao was concerned about transition commitments and she wanted to talk the decision over first with her husband. McConnell's late arrival home delayed Chao's announcement by a few hours. She announced her resignation at 1:36 p.m. on Jan. 7.

McConnell himself would leave the door open to convicting Trump in any future impeachment trial. On the eve of Biden's inauguration, he would also take a giant step further, telling the Senate that the rioting mobs had been provoked by lies. The president and others, McConnell said, had provoked them.

The morning after the deadly riots, Trump showed no remorse as he interacted with his dwindling staff at the White House. By now he was fixating on the perceived disloyalty of Republicans he had believed would do anything for him.

But the president's closest aides understood that his first recorded address released at 4:18 p.m. on Jan. 6, in which Trump told the mob he loved them, was inadequate. Kushner began working on a new draft of what would ultimately become an official Oval Office address at 7:10 p.m. on Jan. 7.

The draft passed through the hands of Kushner, speechwriter Stephen Miller, Meadows, the president's daughter and adviser Ivanka Trump, and White House senior adviser and lawyer Eric Herschmann, among others.

Before Trump gave that speech, the White House made a request to Twitter and Facebook to unlock the president's banned accounts for the purpose of putting out his written press release condemning violence.

The White House also asked the social media companies to temporarily unlock the accounts to distribute video of the speech — finally condemning the attack on the Capitol and requesting no further violence. Trump's staff wanted to use this peace offering to build leverage to get the accounts permanently unlocked. It didn't work. Twitter and Facebook denied that request too.

It had taken everyone 30 hours to drag the president to videotape a speech in which he unequivocally condemned the rioters who had sacked the Capitol in his name.

And it had taken two months to the day to get the president to publicly say the words that had been the obvious reality since Nov. 7: "A new administration will be inaugurated on Jan. 20."

On the 20th, after a blast of pardons, Trump departed the White House at 8:20 a.m. It was a departure in keeping with Trump’s bitter final months. There was no coffee and cake welcome to his successor in the days before, and he would not attend Biden's inauguration. Trump did not once publicly mention Biden's name. Finally, he climbed on board Air Force One for the last time, back to Florida. The reign of President Trump was over.

🎧 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 writing, reporting and research assistance by Zach Basu. It was edited by Margaret Talev and Mike Allen and copy edited by Eileen O'Reilly. Illustrations by Sarah Grillo, Aïda Amer and Eniola Odetunde.