Former US president Donald Trump is seen on a screen during his campaign-style rally in Ohio, US, on Saturday Photo: AFP

One year after the violent assault on the US Capitol, Americans remain deeply concerned about the health of their democracy and about a third say violence against the government can sometimes be justified, according to two polls published Sunday. 

The January 6 attack on the seat of Congress, led by supporters of Donald Trump, was "a harbinger of increasing political violence," and American democracy "is threatened," according to two-thirds of those surveyed for a CBS News poll.

Meantime, Americans' "pride" in their democracy has dropped sharply, from 90 percent in 2002 to 54 percent now, a Washington Post/University of Maryland survey found.

With the January 6 anniversary nearing, the polls offer specific causes for concern: CBS found that 28 percent of respondents believe force can be used to defend the result of an election, while 34 percent told The Washington Post that a violent action against government can sometimes be justified - the largest percentage in decades. The results underscore the seemingly almost irreconcilable views dividing American society, which President Joe Biden - who took office 14 days after the Capitol rioting - has promised to overcome.

On Thursday, he and Vice President Kamala Harris will deliver remarks to mark the one-year anniversary of the assault by Trump's supporters.

Two-thirds of his supporters continue to believe Trump's baseless charge that Biden is not the legitimately elected president.

Trump had addressed thousands of supporters shortly before the Capitol assault, telling them the election had been "rigged" and that they should "fight like hell." 

Some 60 percent of those polled say Trump bears heavy responsibility for the invasion of the Capitol just as lawmakers were set to certify Biden's victory.

There again, opinion follows partisan lines: 83 percent of Trump voters placed his level of responsibility at only "some" or "none," the Post survey found.

And 26 percent of Americans want him to run again in 2024, according to CBS.

A select committee of the House of Representatives has spent months working to establish the roles and responsibility of those who incited or may have organized the protest. 

Despite limited cooperation from Trump's inner circle, the panel has conducted more than 300 interviews and collected thousands of documents.