As time has softened outrage, so it has generated different versions of what happened and why.

The three years since the assault on the Capitol has seen conspiracy theory, misinformation and the emergence - for some - of an alternative truth.

The actual events played out live on TV and have been heavily investigated since, based on extensive first-hand witness evidence. More than 900 individuals have been convicted through the courts for their part in an insurrection.

And yet, a substantial number of Americans call it otherwise. Like demonstrators who marched to the Capitol this weekend, in support of those who descended on the same building three years earlier.

"My view is that there was a set-up," said Tom Jeffries.

"People were tricked into going inside the Capitol building. I think that evidence is coming out more and more every day, and I'm very happy to see that."

Curt Wenger told Sky News: "The doors were opened up, they were let in, they were invited... they weren't even pushing towards the Capitol by the footage.

"They're just standing there and the officers opened the door and let them in."

Nicole Reffitt, whose husband Guy is serving a prison term for January 6 offences, said: "Honestly, I believe that if you look at the full cascade of videos that are out there you will see a much different story."

Micki Witthoeft, the mother of Ashli Babbitt, who was shot dead inside the Capitol on January 6, said of the protesters: "I think they were democracy at its very heart.

"And if you watch the tapes that are about to come out, you'll see the Capitol police attacking American citizens while they're peacefully standing there singing; you'll see them launch ammunitions from overhead."

The alternative view finds an echo across America, particularly among Republicans.

A CBS News/YouGov survey in the days before January 6 this year found that more than a third (37%) of Republicans endorse the conspiracy theory that people who entered the Capitol were mostly people pretending to be Donald Trump supporters.

The same poll found that 20% of Republicans thought that law enforcement officers were trying to encourage the protest.

Most Republicans surveyed said they didn't condone the actions of those who forced their way into the Capitol, but their disapproval has diminished over time - 51% strongly disapproved immediately after the event, now the figure is 32%.

An absolute truth is that perceptions around January 6 will be contested on the campaign trail. Joe Biden has placed democracy at the heart of his election strategy and Trump as its danger.

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In turn, Trump says the same of Biden in his effort to neutralise the line of attack.

Ahead of the election, it will be but one test of truth - though in modern American politics, truth is a relative term.