US President Joe Biden used unusually terse language to lash out at his predecessor and his partisan enablers on Thursday as he marked the one-year anniversary of former President Donald Trump's supporters storming the Capitol.

Biden remembered the Jan. 6, 2021 insurrection as key moment in which American "democracy held," and Trump and his supporters "failed" to undo the nation's will.

“One year ago today in this sacred place democracy was attacked, simply attacked. The will of the people was under assault, our constitution faced the gravest of threats," Biden said from the National Statuary Hall in the Capitol.

"For the first time in our history, a president had not just lost an election, he tried to prevent the peaceful transfer of power as a violent mob breached the Capitol. But they failed. They failed. And on this day of remembrance, we must make sure that such an attack never, never happens again," he added.

The president took particular aim at those Republicans who have continued to downplay the severity of the attack, saying "How dare anyone, anyone diminish, belittle or deny the hell they were put through."

"We saw with our own eyes rioters menace these halls, threatening the life of the Speaker of the House, literally erecting gallows to hang the vice president of the United States of America," he said.

A recent poll from ABC/Ipsos found that while the overwhelming majority of Americans think the insurrectionists posed a threat to the nation’s democracy, a significant portion – 25% – thought the rioters were instead protecting it.

That means that one year after the riot, one in four Americans believe the people who stormed the Capitol were defending the country, opinions likely founded on Trump’s baseless claims of electoral fraud, which he and his allies have continued to disseminate.

The poll did not break down party affiliation for those opinions, but a separate Associated Press-NORC Center for Public Affairs Research survey found that less than 40% of Republicans believe the Jan. 6 attack was extremely or very violent. Nearly 30% believe it was not violent at all.

Those opinions, which have been shared by prominent Trump loyalists, are at stark odds with horrifying video recordings from that day that continue to demonstrate the ferocity of the calamity.

Rioters can be seen crushing an officer in a door frame as he screams desperately for help, throwing objects at police, including a wooden plank and a fire extinguisher, dragging at least one injured officer along the ground, beating others with flagpoles, and using bear spray and pepper spray against them.

Washington, DC police officer Michael Fanone said during congressional testimony in July that he feels “like I went to hell and back to protect them and the people in this room,” expressing a sense of betrayal at those who now seek to minimize the carnage.

While Biden acknowledged that not all Republicans have lined up behind the ex-president and his efforts to cast his 7 million vote electoral defeat in doubt, he said "too many others are transforming that party into something else."

"They seem to no longer want to be the party of Lincoln, Eisenhower, Reagan, the Bushes. But whatever my other disagreements are with Republicans who support the rule of law, and not the rule of a single man, I will always seek to work together with them," he added.

Biden's address drew swift rebuke from some Republicans, including Sen. Lindsey Graham who called it on Twitter "brazen politicization of January 6."

Trump separately responded in a statement, saying Biden's speech was "political theater," and continued to mount the unfounded claims of election fraud which motivated the mob that stormed the Capitol.

During his speech, Biden took aim at Trump's suggestions the election was stolen, maintaining "no election in American history has been more closely scrutinized, or more carefully counted," adding the reason for Trump's continued allegations is that "his bruised ego matters more to him than our democracy or our Constitution."

"There’s simply zero proof that the election results were inaccurate. In fact, in every venue where evidence had to be produced, an oath to tell the truth had to be taken, the former president failed to make his case," he said.