In an extraordinary move, the Republican party officially said Donald Trump’s attempt to overturn his 2020 election defeat and the deadly attack on the US Capitol were “legitimate political discourse”.

A leading Democrat on the House committee investigating the January 6 insurrection said historians would be “aghast”.

The move by the Republican National Committee (RNC) came at its winter meetings in Salt Lake City on Friday, as part of the formal censure of Liz Cheney of Wyoming and Adam Kinzinger of Illinois, the only Republicans on the January 6 panel.

A resolution approved unanimously said Cheney and Kinzinger were engaged in the “persecution of ordinary citizens engaged in legitimate political discourse”.

On January 6, 2021, two weeks before the inauguration of Joe Biden, the US Capitol in Washington was attacked by Trump supporters who the former president had told to “fight like hell” in service of his lie that his defeat was the result of electoral fraud.

The Confederate battle flag was carried into the halls of Congress. Rioters smeared feces on walls. Property was stolen, windows smashed. Members of Congress were hurried to safety. Some rioters sought lawmakers to capture and possibly kill. Some chanted for the hanging of Mike Pence, Trump’s vice-president who resisted pressure to refuse to certify electoral college results.

Seven people died. More than 100 police officers were hurt. More than 700 people have been charged. Eleven members of a far-right militia face charges of seditious conspiracy.

Steve Bannon, a close Trump adviser, has pleaded not guilty to criminal contempt of Congress. Mark Meadows, Trump’s White House chief of staff, could face the same sanction.

Trump was impeached for inciting an insurrection but acquitted by Republican senators. He has repeatedly promised pardons for January 6 rioters if he is president again. He has openly stated that his goal was to “overturn” the election.

Revelations concerning his involvement in events prior to and on January 6 keep coming.

On Friday, the Guardian revealed that Trump personally reviewed a draft executive order concerning the seizure of voting machines in key states and came close to approving the appointment of Sidney Powell, a lawyer and conspiracy theorist, as a special counsel to investigate electoral fraud.

CNN, meanwhile, reported that Trump spoke to Jim Jordan of Ohio, a leading ally House ally, for 10 minutes on the morning of January 6.

What Jordan knew about the Capitol attack and when he knew it remains a central part of the House investigation. Jordan has refused to co-operate. Many expect him to play a prominent role in moves for vengeance should Republicans retake the House in November’s midterm elections.

Newt Gingrich, a former House speaker and candidate for the presidential nomination now advising Republican leaders, has said the party could seek to jail members of the January 6 committee.

Some establishment Republicans have stood up to Trump. Pence, who faces a difficult balancing act ahead of a likely presidential run in 2024, spoke on Friday at a Florida event staged by the conservative Federalist Society.

“President Trump is wrong,” he said. “I had no right to overturn the election.”

Pence also said: “The truth is there’s more at stake than our party or our political fortunes. If we lose faith in the constitution, we won’t just lose elections – we’ll lose our country.”

Mitt Romney, meanwhile, was one of seven Republican senators who voted to impeach Trump in 2021 over the Capitol attack – and the only one to vote to convict in Trump’s first impeachment in 2019, over approaches to Ukraine for dirt on Biden. On Friday, the Utah senator condemned the decision to censure Cheney and Kinzinger.

“Shame falls on a party that would censure persons of conscience, who seek truth in the face of vitriol,” Romney wrote. “Honour attaches to Liz Cheney and Adam Kinzinger for seeking truth even when doing so comes at great personal cost.”

Romney, the 2012 Republican nominee for president, did not mention that the RNC chair, Ronna McDaniel, is his niece. McDaniel stopped using Romney in her name after Trump took power.

Other Republicans in Congress, media reported, sought to avoid discussion of the RNC resolution. Democrats excoriated it. Jamie Raskin of Maryland, a member of the January 6 committee who led Trump’s second impeachment, told the New York Times: “The Republican party is so off the deep end now that they are describing an attempted coup and a deadly insurrection as political expression.

“It is a scandal that historians will be aghast at.”

Rick Wilson, a former Republican strategist now part of the anti-Trump Lincoln Project, said the resolution showed his old party was now a “cult”. Republicans, he said, “don’t get to retcon 1/6”.

The RNC seems determined to try, though it has not yet gone further and kicked Cheney and Kinzinger out of the party, a goal of many Trump supporters.

Kinzinger will leave Congress in November, among Republicans who voted for impeachment who have said they will retire.

He said he had been censured for upholding his oath of office by a party which had “allowed conspiracies and toxic tribalism to hinder their ability to see clear-eyed”.

Cheney, the daughter of the former congressman, defense secretary and vice-president Dick Cheney, faces a Trump-backed challenger endorsed by her own state party.

She said: “The leaders of the Republican party have made themselves willing hostages to a man who admits he tried to overturn a presidential election and suggests he would pardon January 6 defendants, some of whom have been charged with seditious conspiracy.

“I’m a constitutional conservative and I do not recognise those in my party who have abandoned the constitution to embrace Donald Trump. History will be their judge. I will never stop fighting for our constitutional republic. No matter what.”

McDaniel told the Washington Post: “We’ve had two members engage in a Democrat-led persecution of ordinary citizens who engaged in legitimate political discourse. This has gone beyond their original intent. They are not sticking up for hard-working Republicans.”