Rishi Sunak called the prime minister only moments before he went public with his decision to quit. He had told only his closest aides about his decision as he spent the day locked in talks with them. Sources close to the chancellor said it was clear relations with Boris Johnson had broken down over the preparation for a much-trailed joint speech on the economy. But even though it had become increasingly clear they were fundamentally incompatible, it was as the Chris Pincher scandal deepened that MPs most loyal to the chancellor asked him to finally take a stand against the prime minister. Allies of both Sunak and Sajid Javid say they did not coordinate their efforts during the day on Tuesday, though that was the immediate impression given that their tweeted letters came within minutes of each other. It broke just after 6pm as BBC News broadcast a clip of Johnson apologising for appointing Pincher as deputy chief whip. No 10 may have hoped this would be a turning point but as one MP said, it was the classic Johnson playbook. As the clip played out, he made his way to a meeting of his parliamentary loyalists to find ways of shoring up support. Behind closed doors, he mocked his chancellor, saying it would now be easier to deliver tax cuts. But the jokes cannot mask his perilous position. It is the pervasive feeling of being misled, hung out to dry, that has led to the step-change among Conservative MPs over the past 24 hours. The mood has significantly deteriorated in the parliamentary party since the confidence vote. MPs have urged each other to write to the chair of the 1922 Committee, Sir Graham Brady, and ask him to change the rules to allow a new vote before recess on 21 July. Just days ago, it was accepted wisdom there would not be another before the autumn. There are now very few who believe Johnson would win one. “We could get 180 letters within 24 hours if that was needed to trigger a ballot,” the rebel MP Andrew Bridgen said. David Davis, the former cabinet minister, said: “It’s so obvious that the integrity of Number 10 is so fractured that a blind man could see it.” MPs with generous majorities speak openly about losing the next election. “I never really thought there was a genuine prospect of losing my seat,” one Tory MP with a chunky southern majority said. “But now I do think I’m gone. I think there’s no saving it now.” Over the course of the day on Tuesday, MPs said they believed something was about to shift. Whatever goodwill the prime minister retained from his ministers had all but drained away in the course of four days as they were sent out on the airwaves to face questions on Pincher. “I’m fucked if I’m ever doing that again,” one MP confided in a colleague over the weekend. Another minister shrugged when a friendly Labour MP offered commiserations. “I’m going to lose my seat anyway,” they said. Ministers’ calamitous turns on broadcast rounds reached almost farcical levels on Tuesday morning as a remarkable letter dropped from the former Foreign Office permanent secretary Lord McDonald saying Johnson was informed in person about the investigation into Pincher while Pincher was a minister under Johnson in the Foreign Office. Dominic Raab, clearly flustered, said the prime minister had told him the opposite. Later, No 10’s new line was that the prime minister forgot he was told. In a clip released of Johnson’s opening words to cabinet, there was pain etched on the faces of ministers. Another texted: “It’s over” when asked about McDonald’s letter. The anger among even those MPs loyal to the prime minister was so open and pronounced that Johnson went to the Commons tea room on Tuesday afternoon to personally press the flesh. Some MPs were texted to come and see the PM – and refused. Those who saw him said that he told them he had believed Pincher deserved another chance. But all pretence of loyalty was dissolving. At outings in parliament, government ministers were loudly laughed at by MPs as they spoke about the probity of the prime minister. Lord True, the minister in the House of Lords, showed a sense of comic timing as he read out the government statement on standards in public life. He raised his eyebrows and smiled as he recited: “The system is multifaceted; it is made up of interlocking and complementary elements.” Natalie Evans, the leader of the Lords, could not hide her amusement. The statement had been drafted by Michael Ellis, delivered in the Commons with more sincerity several hours earlier. The Conservative benches were barren as Ellis appeared before MPs at 12.30 to answer Angela Rayner’s urgent question on Pincher, replacing a red-faced Raab who had already angrily deflected quizzing from Chris Bryant at justice questions. Ellis was briefly entirely alone on the frontbench as Labour MPs guffawed, but whips ran in to sit beside him, as did the Welsh secretary, Simon Hart, who smiled gamely. Ellis, the Cabinet Office minister who has become the “minister for mopping up”, opened his UQ saying it was a “pleasure to appear before you” – which drew peels of laughter from the opposition benches. Question after question was hostile to Ellis. Conservative MP William Wragg appealed directly to the cabinet. “I ask them to consider the common sense of decency that I know the vast majority of them have, and to ask themselves if they can any longer tolerate being part of a government which, for better or worse, is widely regarded as having lost its sense of direction.” Bernard Jenkin, John Penrose and Jackie Doyle-Price also expressed dismay. But the most serious threat to the prime minister came from the unassuming and loyal MP Caroline Johnson, who had openly backed him at the confidence vote. She questioned why Pincher had ever been given a second chance if formal complaints had been made. “If they were and they were upheld and an apology was given, why were the police not involved and why was he not sacked at the time, never mind given another job?” In the end, it may not be the Sunaks or the Javids who end this prime minister’s tenure. It is likely to be the Caroline Johnsons. And after the resignations of those cabinet ministers, there were more. Jonathan Gullis – a vocally loyal “Red wall” MP who had remonstrated publicly with colleagues over the confidence vote – resigned as a PPS. Kevin Hollinrake, Sally-Ann Hart, Huw Merriman, Bim Afolami – all MPs who said they had backed the prime minister in a confidence vote – backed Sunak or called for Johnson to go. Andrew Murrison resigned as trade envoy. Just weeks ago, he had penned a piece for the Guardian saying Johnson should stay and that his legacy would be a good one. “I would no longer write in those terms,” he said.