Their comfortable and now sustained over months lead in the opinion polls, alongside their habit of demonstrating momentum – the defection of Conservative shadow minister Danny Kruger being the latest case in point – is accelerating the difficult questions and conundrums the other parties wrestle with.

For Labour, the fear that runs to their bones is bequeathing power to an outfit they loathe, Reform UK.

For the Conservatives, frequently leaking defectors to Nigel Farage, every one sharpens the existential questions they confront.

And for the Liberal Democrats, they have a record breaking 72 MPs but are frustrated at a perceived lack of attention, amid the din elsewhere.

Those close to the prime minister are candid about how rough things have been for them and the task they have winning back the trust of so many of their MPs.

“We’re not oblivious to the scale of the problem. We were aware of it before the summer, but the last two weeks have made it more difficult,” is how one senior figure put it.

Another senior figure tells me Sir Keir Starmer’s speech to the Labour Party Conference in a fortnight’s time “will leave people in absolutely no doubt at all what he stands for and what the government stands for”.

That, in itself, is a tacit acknowledgement that from No10’s point of view nowhere near enough people could say what he stands for now.

The argument we are likely to hear is being rehearsed already: the prime minister told Channel 4 News that he has every intention of sticking around as Labour’s leader, and made the case for why:

“I am absolutely determined to lead in this fight of our times between renewal, the patriotic cause of the Labour Party and the division and toxic chaos and decline that would come under Reform.”

What, then, of Kemi Badenoch and the Conservative Party?

My phone rings and it is a former Conservative cabinet minister on the other end.

They say it is “another unsurprising exit” and describe Kruger as “impossible” and an “ideologue”.

But when I bump into another former Conservative cabinet minister they are more pensive at what they fear the defection says about the Tories.

As the Conservatives also approach their annual conference, they confront a moment of peril greater than any in their modern history.

And then there is Reform UK.

Make no mistake, they face colossal questions:

Just for a start, can they build the campaigning infrastructure, the local parties, the list of vetted candidates, the policy heft and attract the talent to present themselves as a viable alternative government?

Then there is the cranking up of scrutiny they will now face, such as this story from the BBC’s Billy Kenber and Phil Kemp.

They are taking on all of this and a lot more in the blink of an eye and it is far from certain it is do-able.

But with each passing month, their opponents treat with increasing credibility the possibility it could happen.

What we witnessing, so often, in other parties right now is their reaction to that.