Support for the January 6 attack on the US Capitol has more than doubled these past two years

US President Joe Biden will on Friday mark the second anniversary of the January 6, 2021, attack on the Capitol, delivering remarks at the White House set to once again condemn an act of democratic vandalism.

He'd just better not ask the American people what they think.

A YouGov poll released on Wednesday found that instead of becoming less popular these past two years, the number of US adults who approve of the Capitol attack has risen markedly.

The shift in attitudes comes despite months of congressional investigations into former president Donald Trump's role in sparking the deadly siege, and as US Capitol Police ready for any potential rerun of the violence this week.

'While most Americans disapprove of the January 6 Capitol takeover, the share who approve has increased significantly since the event first took place,' YouGov said in a statement.

A YouGov poll released on Wednesday found that instead of becoming less popular these past two years, the number of US adults who approve of the Capitol attack has grown markedly

'Two years ago, just 9 percent of Americans strongly or somewhat approved of the takeover; now, 20 percent say they do.'

Perhaps even more startling is who has changed their mind.

The share of Republican voters who now support the riot has grown from 16 percent in the days after the attack to 32 percent this week, according to the survey of 1,500 adults.

But the shift among Democrats has been even more pronounced. Just 3 percent of them approved of the attack when it happened — but that has risen fivefold to 16 percent this week. 

The survey comes ahead of the second anniversary of the attack, when then-President Trump violently breached the Capitol as lawmakers and Trump's vice president, Mike Pence, were set to certify his loss in the 2020 presidential election to Biden, a Democrat. 

It followed a speech in which Trump falsely claimed the election had been stolen.

The assault left five people dead and more than 140 police officers injured.

On Monday, US Capitol Police Chief Tom Manger said his officers were prepared for any possible future attacks, warning of the 'polarized state of our nation'.

The 'current threat climate, particularly against elected officials, will require continued and heightened vigilance,' added Manger. 

A bipartisan House panel investigating the attack said last month that Trump should face criminal charges for his role in sparking the deadly siege. 

Two years ago, just 9 percent of Americans strongly or somewhat approved of the attack on the US Capitol; now, 20 percent say they do, YouGov says

US President Joe Biden will on Friday mark the second anniversary of the January 6, 2021, attack on the US Capitol

In releasing its final cache of documents on Monday, the panel cited security concerns as Congress changes hands, sending some records to the White House and the Department of Homeland Security to review and return to the National Archives

About 900 people have been charged so far with taking part in the riot, including about 470 guilty pleas, according to a tally released last month by the Department of Justice, which is conducting its own investigation into the attack.

While attitudes to the insurrection have shifted over time, attitudes towards Trump's role in the attack have held steady.

At the time, 64 percent of people said he bore at least a little responsibility. Now, 66 percent hold Trump at least in part responsible.

Again, opinion is shifting fastest among Democrats. Just after the attack, 76 percent said Trump bore a lot of responsibility; now, just 69 percent do, according to YouGov.

Biden has slammed the riot as a threat to democracy and the rule of law, but he rarely discusses his predecessor by name publicly and has framed his presidency around uniting and healing a divided nation.

Soon to enter his third year in office, Biden says he intends to seek another four-year term, but has yet to formally his candidacy.

Trump, who never conceded defeat in the 2020 election, has already announced his bid to secure his party's nomination again in 2024.

US Capitol Police Chief Tom Manger this week said his officers were prepared for any possible future attacks on the Capitol, warning of the 'polarized state of our nation'