The Prime Minister faces a crunch vote on her Brexit deal next Tuesday.
She is on course for a heavy defeat – and if it's bad enough Mrs May could feel she has no choice but to resign.
There would then be a power struggle between Labour and the Tories over who should be given the first chance to replace her.
And the choice of the next PM would officially be in the hands of the Queen.
If Mrs May resigned next week, the Tories would install an interim leader while holding an internal election to choose a permanent successor.
The most likely candidate to be a stand-in would be David Lidington, the Cabinet Office Minister who is Mrs May's de facto deputy.
Under normal circumstances, he would then automatically become PM.
But the situation is complicated because the Tories don't have a majority – meaning Mr Lidington would need to ensure he had support from other parties such as the DUP.
Labour also believe that because the Brexit deal is so central to the Government's agenda, the vote should be treated as a confidence motion.
The law states that if the Government loses a Commons vote of confidence, the Opposition must be offered the chance to take over.
That would mean Mr Corbyn becoming Prime Minister as he tries to build a coalition of support in the Commons.
Ultimately the choice of whether the Tories or Labour should get first bite of the cherry will have to be taken by Buckingham Palace.
It is the Queen who formally invites a party leader to try and form a Government.
One insider told The Times: "As the Queen, I would not like to be in this situation. Whatever she does is certain to be controversial."
Whichever leader is chosen would be unable to continue in power unless they could win backing from a majority of MPs.
If neither of them could get a majority within two weeks, Parliament would be dissolved and a snap election would take place in January.
Even if Mrs May doesn't resign, she could face two separate confidence votes – one from Tory MPs and another from the Commons as a whole.
Source: Read Full Article