“We settle our differences at the ballot box.”

Bennie Thompson, chairman of the congressional committee investigating the January 6 attack on the US Capitol, emphasised this article of faith in his opening remarks on Tuesday.

But what followed was a three-hour story about how American democracy, like a rickety old house, creaked and bent and struggled to hold itself together during a thunderstorm of political violence.

There was the tale of an Oval Office meeting that almost ended in fisticuffs. There was testimony from a former true believer in the “big lie” who joined the rampage at the Capitol. There were predictions that if Trump runs again, no one will be safe.

It was a chilling reminder that in a nation that has the genocide of Indigenous Americans, slavery, civil war and relentless gun violence in its cultural DNA, bloodshed is never far from the surface. Since white supremacists marched in Charlottesville, Virginia, in August 2017, extremist groups such as the Proud Boys and Oath Keepers have been ascendent.

Jamie Raskin, another member of the panel, observed: “The problem of politicians whipping up mob violence to destroy fair elections is the oldest domestic enemy of constitutional democracy in America.”

He quoted Abraham Lincoln: “Mobs and demagogues will put us on a path to political tyranny.”

The problem has returned with “ferocity”, Raskin said. “The creation of the internet and social media has given today’s tyrants tools that yesteryear’s despots could have only dreamed of.”

The kindling is always there. The politician who lit it this time was Donald Trump, desperate to cling on to power after losing the 2020 presidential election to Joe Biden.

With options running out, he wanted to mobilise a crowd. Raskin asked: “And how do you mobilise a crowd in 2020? With millions of followers on Twitter, President Trump knew exactly how to do it.”

At 1.42am on 19 December 2020, Trump sent a tweet encouraging supporters to come to Washington on 6 January 2021.

“Be there.. will be wild,” he wrote.

At Tuesday’s seventh hearing on Capitol Hill, the committee laid out what led up to the tweet – and what came in its aftermath.

First, Trump tweeted almost immediately after what has been described as the craziest Oval Office meeting of his administration – a claim that puts it up against some pretty stiff competition. As the former White House aide Cassidy Hutchinson put it in a succinct text message: “The West Wing is UNHINGED.”

The meeting lasted until after midnight with coup plotters including Rudy Giuliani, Michael Flynn and Sidney Powell pushing for the seizure of state election machines by the military, an idea rejected by relatively professional White House staff. Raskin noted a “heated and profane clash” and even threats of a physical fight.

In video depositions, Powell – whom, frighteningly, Trump verbally agreed to appoint special counsel – took a giant swig of Dr Pepper. Giuliani recalled telling Trump’s advisers: “You’re a bunch of pussies.”

It was as if the aggression in the hallowed Oval Office radiated outwards across the country, activating a Trump army ready to wage war on democracy. His post-meeting tweet was, the committee member Stephanie Murphy noted, “a call to arms”.

The hearing saw videos and social media posts from Trump supporters: “Is the 6th D-Day? Is that why Trump wants everyone there?”

“Trump just told us all to come armed. Fucking A, this is happening.”

“It ‘will be wild’ means we need volunteers for the firing squad.”

One Trump supporter promised there would be “a red wedding going down January 6” – a reference to a Game of Thrones scene where many attendees are slaughtered.

Slowly but surely, as in previous hearings, the committee joined dots that always lead back to Trump. They cited his infamous presidential debate advice to the Proud Boys: “Stand back and stand by.”

In a video deposition, a Twitter employee testified that there had not been such direct communication between the president and far-right groups before, and they saw this as asking to join in fighting for his case on January 6. One user responded to the tweet: “Locked and loaded and ready for Civil War Part Two.”

Raskin noted how the tweet motivated the Proud Boys and Oath Keepers, groups which had not historically worked together, to coordinate their activities.

The committee obtained thousands of messages that showed strategic and tactical planning. It displayed photos of Flynn palling around with the Oath Keepers and the pro-Trump dirty trickster Roger Stone communicating with both groups.

It also displayed a draft tweet to allege Trump was planning well in advance to tell supporters to march on the Capitol. It was damning and at times sickening, even before the vice-chair Liz Cheney’s sting in the tail, revealing Trump had personally tried to call an unidentified committee witness.

But did this hearing close the case against the former president? There are echoes of the Russia investigation, with plenty of suspicious contacts and common goals but not the direct evidence of collusion that might, in a simple headline, persuade Trump supporters he issued orders to militia groups.

Mick Mulvaney, a former Trump White House chief of staff, tweeted: “I’m sorry, but if a bunch of nut jobs think Trump was calling them to riot, that doesn’t mean he was. Using that theory, the Beatles were responsible for Charles Manson. This is sensational (is that the purpose?), but without some connection to the [White House], it is only that.”

The convergence of interests between Trump and the extremists was inescapable, however. The witness Jason Van Tatenhove, a former spokesman for the Oath Keepers, cut to the chase: “I think we need to stop mincing words and just talk about truths … What it was gonna be was an armed revolution … This could have been the spark that started a new civil war.

“I think we’ve gotten exceedingly lucky that more bloodshed did not happen … I do fear for this next election cycle because who knows what that might bring.”

It is a valid fear in a political climate where in recent weeks a former judge was killed in Wisconsin, a man was charged with attempting to murder the supreme court justice Brett Kavanaugh and a Republican candidate for Senate in Missouri, Eric Greitens, ran a campaign ad in which he storms a building with a gun to hunt moderates of his own party.

Thompson and others have cause to worry about whether differences will be settled at the ballot box next time, especially if Trump avoids prosecution and runs for president again.

In a closing speech for the ages, Raskin argued that Trump is dragging the Republican party into an authoritarianism that thrives on political violence. Alluding to Trump’s inaugural address, Raskin said: “American carnage. That’s Donald Trump’s true legacy … The Watergate break-in was like a Cub Scout meeting compared to this assault on our people and our institutions.”

Describing American democracy as a “precious inheritance”, Raskin concluded: “We need to defend both our democracy and our freedom with everything we have and declare that this American carnage ends here and now.

“In a world of resurgent authoritarianism, racism and antisemitism, let’s all hang tough for American democracy.”