The biggest factor keeping Theresa May in office is the absence of an alternative Conservative leader with broad enough backing in the party to be crowned her successor, without causing a messy contest that could destabilise the party and put it out of power.
That is why some Tories are grimly resigned to Mrs May limping on until 2019 or so, when they hope Brexit talks may have come to something resembling a conclusion.
But there is an alternative scenario emerging. Philip Hammond is increasingly seen by some colleagues as the man to replace Mrs May in a relatively smooth and bloodless transition later this year.
The Chancellor’s name has come up in several conversations I’ve had with Conservatives this week. Even old foes are wondering if he is the best alternative to sticking with a badly wounded PM for two long, dangerous years.
An alternative scenario might look something like this: over the summer recess, Mrs May is ‘persuaded’ by senior colleagues that her time is up. Her decision is confirmed in September and Mr Hammond is anointed her successor, his coronation confirmed at Tory conference in early October.
Mr Hammond, perhaps with David Davis as his Deputy PM and Brexit negotiator, sees the UK through the exit talks as a caretaker PM, then announces a full leadership contest in 2019 or 2020 to decide who leads the party into a (possibly early) election where the Tories seek approval for that Brexit deal. (Whether Mr Hammond would stand in that contest varies according to who you talk to: some Tories would only accept this on the condition he didn’t try to keep the crown they’d hand him.)
Such a scenario would delight many business leaders, who see Mr Hammond as a grown-up with a realistic approach to Brexit and a commitment to a formal transition after EU membership ends.
Tory Leavers might not be so calm however: they see Mr Hammond as pushing for a Brexit that would leave Britain entangled in the EU for years to come and possibly permanently. Expect men like Iain Duncan Smith to rally to Mrs May’s cause if the Hammond talk turns into action.
It’s also unclear whether the others who might seek the crown would accept that scenario. Mr Davis agrees with Mr Hammond on many Brexit issues and might be willing to sign up. But Boris Johnson? Some of his friends believe his best bet is indeed a contest in 2019 or later, but he may think his chances are better if Mrs May clings on a while yet before succumbing to the inevitable.
Likewise the younger generation of would-be leaders. All have to calculate whether Mr Hammond would really serve as a caretaker before stepping aside, or try to keep the job as long as possible.
There’s also the minor matter of what voters would make of all this.
A Hammond coronation is, like much else these days, far from certain. But today at least, it looks like the most plausible alternative to the Conservative Party stumbling through some of the most consequential years in modern British history with a PM it doesn’t want or believe in.