Key to Boris Johnson’s fate in the coming hours or days will be whether the point is reached when 54 Conservative MPs hand letters of no confidence to the 1922 Committee.
While a significant blow to his authority, the letters in themselves will not be enough to unseat the British prime minister.
They will trigger a vote of confidence on his leadership, with a simple majority required from the 360 Conservative MPs to keep or remove him from office. Indeed, if the numbers reach close to the 180 needed for dismissal, Mr Johnson may regard this as significant enough to resign.
Thus the vote in itself is a moment of extreme jeopardy and unpredictability, especially given that 101 MPs rebelled against the lockdown rules vote just before Christmas.
What is the 1922 committee?
Unique to the Tories, the 1922 Committee, formally known as the Conservative Private Members' Committee, was set up in 1923 to represent backbenchers from the 1922 election intake of MPs.
Its day-to-day role is to support MPs who are not in government and it meets every week when the Commons is sitting.
But the “trade union” of MPs can wield exceptional influence by effectively backing or sacking its leader, either when in opposition or in power.
It was to the 1922 Committee that Mr Johnson appealed before the lockdown vote in December to win MPs over. The sign of his ebbing authority came after so many listened to but then rejected his pleading.
Sir Graham Brady, 54, has been its chairman since 2010 and it is to his corner office on the fourth floor of Portcullis House, the MPs workplace adjacent to Parliament, that at least seven MPs have publicly stated they entered to hand in their papers.
Why do 54 letters matter?
If the 54 is reached, Sir Graham will oversee the process of a leadership ballot. The last time he did so was in December 2018 when Theresa May was challenged during her excruciating attempts to push Brexit through Parliament, with Mr Johnson among the ringleaders pushing for her downfall. She survived the vote by 200 to 117, and the rules meant she could not be challenged for at least another 12 months.
Despite that ruling, by May 2019 she had resigned after a collapse in support from her Cabinet.
A few months later, Mr Johnson replaced her after an election contest, whereby, following a series of ballots, MPs selected two candidates for election among the Conservative members.
Up against the honourable, capable but not quite as charismatic Jeremy Hunt, Mr Johnson won 92,000 members' votes to his rival's 46,000 and became Conservative leader and thus prime minister.
That the Conservative leadership elections are being discussed so intently once again demonstrates the extraordinary transition from less than three months ago, when Mr Johnson looked untouchable, to the diminished figure who conducted a painful 15-minute interview with Sky’s political editor on Tuesday.
When will the confidence vote happen?
The “partygate” allegations of Downing Street drinking sessions breaching the very lockdown rules it set could yet unseat Mr Johnson. All attention is now on the publication of the report by Sue Gray, the civil servant in charge of investigating the parties.
It will be for MPs to judge whether the opprobrium towards Mr Johnson justifies a letter to the 1922 Committee. But that ominous figure could yet be reached before Ms Gray’s report is published in the coming days.
A cabal of the 2019 intake of MPs, labelled the “Pork Pie plotters” because one of its members represents Melton Mowbray, home to the snack, might yet tip the balance to reach 54.
The latest Channel 4 News polls published on Wednesday show Labour leading by a significant 11 percentage points. The opposition's standing was further enhanced when Christian Wakeford, a Conservative MP from 2019 “Red Wall” intake defected to Labour.
Mr Johnson could soon find himself standing awkwardly in a Westminster corridor awaiting his fate, much like Mrs May did three years earlier. He will not be counting on her sympathy – or her vote – if it comes to that.
How is Boris Johnson fighting for his job?
The prime minister has opened a number of fronts in his defence, including a series of policy announcements, under the banner “Operation Red Meat”, designed to appeal to party members.
They include a proposal to scrap the BBC licence fee, which funds the service and is regularly a target of Conservative ire.
Planned reforms to the asylum system are also going through Parliament, which are designed to be tough to appeal to the pro-Brexit anti-migration faction, but which are also criticised as breaking international laws on the rights of asylum seekers.
With his reputation harmed by the sour taste of the lockdown rules being broken, Mr Johnson has apologised for lapses in judgment. He can also use the good news fillip of lockdown restrictions being lifted as a weapon in the fight to keep his job.