But one problem she does not have to worry about just yet is her main rival political parties.
The Labour Party under Jeremy Corbyn is so radical, and also so bitterly and openly split, that it is hard to see it posing much of an electoral challenge for a long time.
The Liberal Democrats were so badly hit in the general election last year that they have very few MPs to fill their senior positions and have ended up with an eccentric leader who is also unlikely to pose much electoral threat (unless the party revives in an anti Brexit backlash from moderate Remain supporters who want to rally round a party to punish the Tories).
And then Mrs May can also breathe easy over any threat from Ukip, which has been a shambles since the departure of Nigel Farage (despite him stepping back in as interim leader).
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Under his stewardship the party, arguably, was principally responsible for changing the course of British history, by helping to establish support for Brexit, and then galvanising it.
In the process, Mr Farage’s political insurgency helped to spook David Cameron into an In-Out EU referendum pledge, victory in which in June could yet cause the EU to implode.
But there has been no-one even approaching a credible successor to Mr Farage.
Douglas Carswell, the party’s only MP, seems to have disastrous relations which much of the high command. He pushes a liberal and cosmopolitan world view that is utterly at odds with the rank and file.
Diane James and then Steven Woolfe had some personal qualities that might have made them passable as Ukip leaders, as did others such as Suzanne Evans. But none of them even come close to having the punch and charisma of Mr Farage. Unless he abandons his determination to retire, or some other barely known figure emerges, it is hard now to see the party surviving as a significant political force.