Somewhere in Bedminster, New Jersey, on Thursday afternoon, it seems quite possible that an elderly man was sitting in front of a television howling with rage.

Donald Trump, who spends summers at his Bedminster golf club, is a TV guy, a ratings guy. So the widely televised hearings of the congressional committee investigating the January 6 attack on the US Capitol hit him where it hurts.

The former US president has reportedly been glued to them – and has not liked what he’s seen. As the panel has presented a carefully crafted case against Trump as the leader of a failed coup, he is said to be livid that there is no one in the room to speak up for him.

Trump “has tuned into every hearing” and has grown increasingly irate – to “the point of about to scream at the TV”, according to a close adviser – with what he views as the “lack of defense by his Capitol Hill allies”, the Washington Post reported.

He is possibly aware that, while the hearings come too late to force his resignation and may or may not cause the justice department to press criminal charges, they seem to be inflicting greater political damage than anyone imagined.

Thursday’s fifth hearing served up more of the same in the Cannon Caucus Room which, somewhat reminiscent of a grand ornate ballroom with curtains closed and lights on, is bringing a gravitas to the nailing of Trump that no trickle of media revelations or tell-all memoirs can.

Photographers crowded around the witnesses just as the panel’s chairman, congressman Bennie Thompson, brought down the gavel, a now ominous sound for Trump, and spoke of “a brazen attempt to use the justice department to advance the president’s personal political agenda”.

Trump’s consternation is likely to have only intensified when Republican Liz Cheney summed up his central role in the conspiracy to overturn the election, then another Republican, Adam Kinzinger, questioned former justice department officials. “Today President Trump’s total disregard for the constitution and his oath will be fully exposed,” Kinzinger said.

Once again, all went smoothly and efficiently. There were no interruptions, objections, points of order or spoiling tactics. And that is said to have made Trump furious. He is especially critical of Kevin McCarthy, the minority leader in the House, for boycotting the committee instead of giving pro-Trump Republicans a voice on it.

Trump told Punchbowl News, “In retrospect, I think it would have been very smart” to put more Republicans on the committee. “The Republicans don’t have a voice. They don’t even have anything to say.”

McCarthy apparently gambled that this would allow Republicans to write off the hearings as illegitimate, partisan and an attempt to distract from more pressing issues such as inflation. But the presence of Cheney, Kinzinger and more than a dozen Republican witnesses have undermined that argument.

Moreover, McCarthy, who wants to be speaker of the House of Representatives, may have forgotten that Trump pays attention to TV, where the hearings are inescapable and will run into next month, prolonging the agony. Even if they are not penetrating the Trump base, they are penetrating Trump himself.

And his formidable political instincts – which served him well against Hillary Clinton and warned him early that Joe Biden posed the biggest threat to his reelection – will now be warning Trump that the January 6 committee’s contribution to the history books poses a threat to his hopes of a 2024 presidential run.

The hearings have painted a portrait of a man detached from reality, peddling paranoid conspiracy theories and putting himself before his country. Kinzinger noted: “He was willing to sacrifice our republic to prolong his presidency. I can imagine no more dishonorable act by a president.” They have also highlighted a callous, cruel streak that saw him make baseless allegations with no regard for how they would ruin individual lives.

A source close to Trump told NBC News: “I look at this and say there is nobody in America who is watching this – even with all that’s going on in the world with Joe Biden – and saying, ‘Donald Trump should be the next president of the United States’. Nobody.’”

Trump’s chequered record of endorsements in this year’s Republican primary elections have also raised questions over whether he still has a tight grip on the “Make America great again” movement. The hearings could turn him into damaged goods and give even Maga diehards some reasons to look for more electable alternatives.

Frank Luntz, a political consultant and pollster, said: “I see people no longer drinking the Kool-Aid. I see people moving away from Trump for the first time. His endorsement matters more than anybody else in the Republican party by far, but he does not control the Republican party anymore. He’s the loudest voice, he has the most influence, but he’s losing control every day.”

The leading challenger to Trump’s throne is Ron DeSantis, the rightwing governor of Florida, who is gaining on him in opinion polls. A poll of 300 likely Republican voters in New Hampshire, the first presidential primary state, found 39% wanted DeSantis to be the next nominee, while 37% favored Trump, within the 5.5% margin of error, according to the University of New Hampshire Survey Center.

Pam Roehl, attending last week’s Faith & Freedom Coalition conference in Nashville, Tennessee, told the Associated Press that she still supports Trump but increasingly finds herself in the minority among friends who have moved on. “They’re like kind of: ‘Get with the program. Why aren’t you backing DeSantis?’” she was quoted as saying.

If the two men go head-to-head, DeSantis could point to his legislative record in Florida and would be free of the baggage of the 2020 election and the January 6 insurrection. More than three decades younger than Trump, the governor would be seen as the candidate of the future while the former president keeps harping on the past. Trump’s big lie, it transpires, could prove his big liability.