Theresa May is facing the political battle of her life in the wake of the twin shock resignations of David Davis and Boris Johnson.
Tory MPs are threatening to oust her from the top job, while speculation has renewed that she might quit and walk away from her divided party – and country.
Her departure may spark a bitter Tory leadership contest which could see the Remainer and Eurosceptic wings of the party compete for the top job in a brutal campaign.
If the warring Conservatives do not call a truce then they could march Britain back to the polls for the third major national vote in three years.
This could pave the way for Labour’s hard left leader Jeremy Corbyn to slip into Number 10 – a scenario Tories warn would spell disaster for the country.
Any leadership contest would be likely to leave Mrs May’s Brexit plans in tatters – throwing the crunch talks into crisis and fuelling calls for another referendum.
Here are some of the scenarios which could happen if Mrs May is ousted from No10.
Theresa May could be toppled in two ways. Furious Brexiteers on her backbenches could mutiny and call a leadership contest if 15 per cent of them (currently 48 MPs) write to the chairman of the 1922 Committee Graham Brady saying they have no confidence in her.
This would trigger a leadership contest which, if she lost, would force Mrs May out of No10 in a humiliating end to her political career.
The contest could pitch Tory Remainers against Brexiteers in a brutal competitions which would lay bare the gaping chasm between the two warring wings – leaving wounds which could take some time to heal.
The winner could be installed at Downing Street without having to go to a national vote in a General Election – just as Mrs May was after David Cameron quit after losing the referendum in 2016.
Even if Mrs May is not forced out by a vote of no confidence from her MPs, she could decide that she has had enough of her warring Cabinet and mutinous backbenchers and quit.
This would also allow her Tory successor to take up the reins of power without a General Election.
Whoever succeeds her faces the mammoth task of uniting the Tory party while coming up with a Brexit plan which Britain’s voters, Parliament and Brussels can all sign up to.
If Theresa May is ousted via a no confidence vote or sensationally quits, the Tory party may find itself so bitterly divided they decide to call another General Election.
Bookies have slashed the odds of another election being held this year – with Ladbrokes cutting their odds from 11/2 on Sunday night to 5/2 today.
This would be the third major national poll in three years – after the EU referendum in 2016 and Mrs May’s disastrous snap election last year.
British voters tend to punish divided parties at the ballot box, and many Tories are terrified that an election could let hard-left Labour leader Mr Corbyn slip into power.
Conservatives will be extremely reluctant to take the gamble and return to the polls just a year after angry voters stripped them of their majority.
But if the warring factions within the party cannot strike a compromise, then they may be left with no choice.
Even if Tory Brexiteers revolt and call a vote of no confidence in the PM, she may rally enough support to survive it.
Many Conservatives have urged their party colleagues to stop swiping at get behind her to make a success of Brexit.
But any leadership the battle will have dealt a major blow to her already beleaguered authority and would almost certainly mean she would quit after delivering Brexit rather than stay on and fight another General Election.
Remainers who are determined to stop Brexit have swooped upon the bitter war raging at the top of Government to demand a second referendum.
They claim that if Tory ministers cannot agree a deal then they cannot expect the British public to sign up to it either.
Many Brexit voters will feel betrayed if their historic vote in 2016 is effectively picked apart by politicians – and commentators have warned that it will only fuel anger and disenfranchisement with the political class.