By almost all accounts, Boris Johnson would never take it upon himself to resign as prime minister.
Even with a police investigation looking into partygate hanging over him, the prime minister is holding on to power, claiming the public want him to focus on their priorities.
That leaves those who want rid of him just two hopes; a general election or a vote of no confidence.
With the next general election not scheduled to take place before 2024, the other option is more likely.
Around 20 letters are understood to have been submitted but the authors are allowed to remain anonymous and most have chosen not to reveal themselves.
Here is a list of Tory MPs who have publicly announced that they've submitted a letter of no confidence:
Sir Gary Streeter - MP for South West Devon
Anthony Mangnall - MP for Totnes and South Devon
Tobias Ellwood - MP for Bournemouth East
Peter Aldous - MP for the Waveney constituency in Suffolk
Andrew Bridgen - MP for North West Leicestershire
Douglas Ross - MP for Moray and leader of Scottish Conservatives
Sir Roger Gale - MP for North Thanet
Aaron Bell - MP for Newcastle-under-Lyme
Nick Gibb - MP for Bognor Regis and Littlehampton
How can they trigger a vote of no confidence?
Fifteen percent of the parliamentary party - 54 MPs under this Parliament - must support a vote of no confidence in order for one to be triggered - unless the PM calls one himself.
MPs register their support for a no confidence vote by submitting letters to to the 1922 Committee, which is effectively the HR division of the Tory party which represents its backbenchers.
Once the threshold is reached an announcement will be made by the committee chairman, Sir Graham Brady.
He keeps the number of letters - and the senders - secret until he receives 54.
A vote of no confidence will be held, with Tory MPs asked whether or not they have confidence in their leader.
A simple majority wins: If more than 50% of MPs want Mr Johnson to remain in post he will be immune from another leadership challenge for another year.
If he loses then hopeful contenders will announce their intentions to replace him. Names on the ballot paper will be whittled down in rounds of voting by MPs until only two remain.
There will then we a month of campaigning before members of the Conservative Party vote to elect a winner.