This was the week in which the Tory party – from cabinet ministers down to grassroots associations – started to believe that the end was nigh for Boris Johnson’s premiership.

“The problem is that he has in no way accepted that himself,” says one senior Tory adviser with knowledge of the prime minister’s inner circle.

And so began a period of what one Conservative minister described as prime ministerial “purgatory” – the gap between a leader being politically done for and the moment of their stepping down.

Downing Street had hoped to draw a line under the partygate scandal in the new year, after a grim run of headlines and mutinous mood in the Tories before Christmas.

But after only a brief respite, the bad news for Johnson resurfaced on Monday night when ITV revealed that Johnson had attended a “bring your own booze” social event in the garden of No 10 to which 100 people were invited. On Wednesday, he had to say sorry in the House of Commons, while several prominent Tories called for his resignation.

By Friday morning, Downing Street even found itself apologising to the Queen after it emerged that two other parties were held in No 10 on the eve of Prince Philip’s funeral, while the prime minister was away at Chequers.

However, some of those who have spoken to Johnson this week say he is not in a mood to give in to what many Tory MPs now see as inevitable.

One person present at cabinet on Tuesday said the mood in No 10 was “total denial” about the seriousness of the situation that Johnson faces. Describing a “bizarre” and “farcical” virtual meeting, they said not a single cabinet minister mentioned the political peril that Johnson is facing, as Rishi Sunak, the chancellor, gave a presentation on the economy, and Sajid Javid, the health secretary, an update on Omicron.

The fact that no one was willing to confront the prime minister about how he will dig his way out of the current hole may indicate that cabinet colleagues have already turned their minds to whatever is next – and which of them is best placed to succeed him.

However, while most Tory MPs now believe Johnson will be gone before the next election, there is heated disagreement about the best timing for his departure. The clearest way of challenging the prime minister would be for 50 or so MPs to hand in letters of no confidence in him to the 1922 Committee of backbenchers.

But some of Johnson’s opponents are worried there is a risk that he could still, despite everything that has happened, secure enough votes among his colleagues, which would mean he would be safe for another year.

MPs said another part of the reason for delaying a challenge would be that the leadership teams of possible opponents – such as Sunak, Liz Truss, Jeremy Hunt and Javid – do not yet feel completely ready for a contest.

They may look at the economic pain on the cost of living about to be inflicted on the country this spring and believe that it would be better to keep Johnson in place for a while longer to “suck up that unpopularity”, said one MP. A no confidence vote would only be likely to succeed with the tacit support of cabinet leadership candidates and the MPs on their list of supporters.

Then there are the veteran MPs who have seen prime ministers weather some terrible times and believe the party should hold fire until they have seen whether public anger subsides and the polls settle again, potentially using the local elections as a barometer.

Others disagree and believe that it would be harmful to have a lame duck prime minister in place for much longer, and wrongheaded to risk the loss of council seats, arguing that the moment of reckoning should come sooner. This caucus – comprising many more centrist Tories as well as some 2017 and 2019ers worried about their seats – are pushing for a challenge after the publication of Sue Gray’s report into the parties at No 10 during lockdown, which could be published at the end of next week.

MPs said there will be “phone calls and Zooms” in the next few days where they work out their strategy and whether that is the right moment to seek a confidence vote in Johnson’s leadership.

Many MPs are also using the weekend to sound out their constituents and associations.

One 2019 Tory MP, Lee Anderson, sent out a message asking people for their views, with a survey of options for people to complete, asking: “a) He has done wrong and apologised. It is time to move on. b) He has done wrong and should go. c) He has done wrong and should have a six-month departure plan.”

Setting out his own position, Anderson said: “Personally, I would not back anyone who has knowingly done wrong but I also realise that our country is at a critical point in beating the virus.”

Other Tory MPs have written to constituents saying they believe Johnson’s position would be untenable if the Gray report finds serious wrongdoing. But in private, some MPs believe the bar is lower and that he could be pushed out if any new revelations emerge in the Gray report that implicate him in the partying culture. There is also a fear that photos, videos or new disclosures could appear at any time in the media.

While backbenchers may be the ones to implement a challenge, the mood of the cabinet will be key. The least supportive has been Sunak, who issued a statement backing his apology but was marked by its absence of any other supportive comments.

But several cabinet ministers still believe Johnson may still be able to find way of turning things around. His greatest defenders among senior colleagues have been Priti Patel, the home secretary, and Nadine Dorries, the culture secretary.

Others are reserving judgment until they see how he reacts over the next week or so – and particularly in relation to whether he will show he is willing to overhaul his operation.

Colleagues accept that he is a “campaigner, not a manager”, and that he needs better support in No 10, says one cabinet minister.

“Boris is staring disaster in the face in a way that he hasn’t done before in his premiership,” he says. “But if anyone on the planet can come back from this, it’s Boris. He does have the characteristics that defy normal expectation.”