Alabama congressman and once-zealous Trump supporter, Mo Brooks, has a remarkable new stance on the political future of his former hero. “It would be a bad mistake for the Republicans to have Donald Trump as their nominee in 2024,” he said.

The stark judgment from Brooks was indicative of the deepening and brutal blame game among Republicans which continued on Monday, nearly a week after the party failed to retake Congress in the midterm elections and a day before Trump’s expected announcement of a new presidential campaign.

Speaking to AL.com, Brooks, an Alabama congressman, added: “Donald Trump has proven himself to be dishonest, disloyal, incompetent, crude and a lot of other things that alienate so many independents and Republicans. Even a candidate who campaigns from his basement can beat him.”

That was a reference to Joe Biden and his precautions against Covid in the 2020 election the Democrat won by more than 7m votes and 306-232 in the electoral college.

Brooks did not accept that result. On 6 January 2021, he donned body armor and spoke to Trump supporters at a rally near the White House. Repeating Trump’s lie about electoral fraud, he said: “Today is the day American patriots start taking down names and kicking ass.” The mob then attacked the Capitol, a riot now linked to nine deaths including suicides among law enforcement.

The election subversion Brooks supported is under investigation by the House January 6 committee, the Department of Justice and state authorities. But Brooks broke with Trump earlier this year, when the former president rescinded his endorsement for US Senate, because Brooks publicly urged him to stop re-litigating 2020.

Trump’s eventual endorsee in Alabama, Katie Britt, won a Senate seat. But elsewhere last Tuesday high-profile Trump-endorsed candidates failed, ensuring Democrats held the Senate and stayed on course to hold the Republicans to a tight House majority.

Trump is almost certain to announce his 2024 run at his Mar-a-Lago resort in Florida on Tuesday. But the fire from his own party keeps coming, the barrage widening to include shots at leaders in both houses of Congress.

In the Senate, Marco Rubio of Florida, who retained his seat against a highly-rated Democrat, Val Demings, tweeted: “The Senate GOP leadership vote next week should be postponed.”

Josh Hawley of Missouri, a potential challenger to Trump in 2024, added: “Exactly right. I don’t know why Senate GOP would hold a leadership vote for the next Congress before this election is finished.”

That was a reference to the runoff for the last Senate seat to be decided, in Georgia and between the Trump-endorsed Herschel Walker, a controversial former NFL star, and the incumbent Democrat, Raphael Warnock. Warnock won a tight vote last Tuesday but did not pass 50%, teeing up the runoff.

Victories in Pennsylvania – the only Senate seat to flip so far – Arizona and Nevada mean the Democrats will control the Senate even if Warnock loses, thanks to the casting vote of the vice-president, Kamala Harris.

The other Florida senator, Rick Scott, is under pressure after leading the Republican election effort. The party leader in the Senate, Mitch McConnell of Kentucky, is also feeling the heat.

On Tuesday, Josh Holmes, a Republican operative who was formerly chief of staff to McConnell, told the Wall Street Journal the Senate campaign “was run basically as a Rick Scott super Pac, where they didn’t want or need to input any Republican senators whatsoever. That’s a huge break from recent history where members have been pretty intimately involved.”

Democrats seized on an “11 Point Plan to Rescue America” Scott issued earlier this year, in which the senator, widely thought to have presidential ambitions of his own, proposed that more Americans pay federal income tax and said Congress could “sunset” social security and Medicare within five years.

Holmes said McConnell told Scott: “When you are in leadership you don’t have the ability to do something like this without other people carrying your water.”

In the House, the defeat of the Trump endorsee, and election-denier, Joe Kent in Washington state quickly came to seem symbolic of Republican failures.

In the primary, Kent defeated a six-term incumbent, Jamie Herrera-Beutler, who suffered for being one of 10 House Republicans to vote to impeach Trump for inciting the Capitol attack. Kent went on to lose the seat, to the Democrat Marie Gluesenkamp Pérez.

The House Republican leader, Kevin McCarthy, faces a growing threat from the far-right of the party, jeopardising his hopes of becoming speaker should Republicans take control of the House.

Andy Biggs of Arizona, another congressman investigated for his support of Trump’s attempt to overturn the 2020 election, is reported to be teeing up a challenge to McCarthy.

Adam Kinzinger of Illinois, like Herrera-Beutler a Republican who voted to impeach Trump, announced his retirement rather than face a primary defeat then went on to sit on the House January 6 committee.

Amid post-election recriminations on Capitol Hill, he tweeted: “To GOP’ers: if Kevin McCarthy had not gone to Mar-a-Lago, had the Senate convicted, or had any more congressmen actually stood on principle, likely we would have no Trump, the alt-right would be a sick memory, and you could look in the mirror.

“Just FYI. Maybe start now.”