The resignations of cabinet ministers at the time of the Chequers plan last July, and again, when Mrs May secured her deal with the EU in November, might also have brought an end to her premiership.
And losing the first Commons vote on her deal by the biggest majority in parliamentary history was certainly an occasion when other prime ministers would have felt they had to step down.
But the extraordinary political situation which has existed in the UK since the EU referendum, and Mrs May’s single-minded stubbornness in her determination to deliver Brexit at almost any cost, has seen her cling onto power despite the storms raging around her.
And now she seems to have survived another potential ousting. Mrs May’s ill-judged speech inside Downing Street on Wednesday, explaining the delay to Brexit and blaming MPs, caused fury among the very people whose support she needed to win for a third “meaningful vote” on her deal.
And the Sunday papers were full of plots and conspiracies to force the Prime Minister to quit.
De facto deputy David Lidington and Environment Secretary Michael Gove were touted as stand-in replacements pending a full Conservative leadership contest at a later date.
One paper claimed 11 cabinet ministers wanted Mrs May to make way for someone else and were planning to confront her at yesterday’s cabinet meeting, threatening mass resignations if she refused.
But the predicted rebellion fizzled out and the Prime Minister lives to fight another day, though uncertainty remains over her longer-term future. In order to survive the Conservatives’ vote of confidence in December, she was forced to declare that she would not lead the party into the next election on the scheduled date in 2022, even though “in her heart” she wanted to do so.
Now MPs are said to want a guarantee she will not lead the next phase of Brexit talks, on future relationships with the EU.
Tory Party rules mean Mrs May cannot face another motion of no confidence until December. Pundits say senior party figures – who used to be referred to as “men in grey suits” – could still make it clear to her that it was time to go.
But if the Prime Minister is true to form she would no doubt try to rebuff these messengers of her doom. Her whole record is of refusing to be diverted from what she sees as her mission.
In what seems to have been intended as a supportive comment, Dutch prime minister Mark Rutte likened Mrs May to the Black Knight in Monty Python and the Holy Grail.
“I have every respect for Theresa May,” he said in an interview. “She reminds me occasionally of that character from Monty Python where all the arms and legs are cut off but he then tells the opponent, ‘Let’s call it a draw’. She’s incredible. She goes on and on.”
But determination does not always win the day.