Can any Tory candidate really challenge Boris Johnson? asks Robert Peston

Boris Johnson will be very hard to stop in his pursuit of the Tory leadership crown. Credit: PA

Now the real shenanigans begin.

Boris Johnson will - barring a disaster of Johnsonian scale - be in the ballot of Tory members to pick their next leader and our prime minister on or around 22 July.

And, truthfully, given that he is by a margin the darling and chouchou of those members, it is challenging to see how he can be beaten.

Except for one thing.

Who will get to the let resident cat Larry in and out of No.10? Credit: PA

His campaign has been wholly based on Boris Johnson as an idea, a concept - the idea being that only he through his force of personality and penchant for the arresting bon mot can sequentially deliver Brexit, boost the popularity of his party and then win a general election.

His fans care not the most withered of figs for his chequered record at the Foreign Office, his joke that many found offensive about Muslim women wearing the veil, the notorious mismatch between his confidence and his grasp of detail.

He is the Tories' Trump - which his supporters gleefully swagger about in private, and puritanically deny in public.

As one of his cheerleaders said to me: "The whole point about Boris is that no one quite knows what he'll do next, and that is precisely what we need in this our lowest point in history - because it is only through nonplussing, confusing and scaring our opponents, especially those in Brussels, do we have any chance of leaving the EU in the autumn."

Well maybe.

But as Amber Rudd, from the Hunt campaign, said to me just now, Boris cannot get to the finishing post purely as a political hologram: at some point the real Boris Johnson will - surely - face forensic questioning, in broadcast hustings and longer TV interviews.

And that is where she - and Gove supporter Anne Milton - think it is just possible that Johnson will come unstuck.

Because for all his dynamism from the pulpit, he is rarely at ease when interrogated on the small print, and even occasionally on the bigger typeface too (Boris-backing Priti Patel's remarks on my programme last night that "Boris won't make mistakes as prime minister" is one of the quotes of the campaign).

From which there follows a very simple question: which of the six remaining candidates is best place to turn the ballot of members into a serious contest rather than a national victory lap for Johnson?

It is unlikely to be Dominic Raab, for the reason that his views on the only issue that matters, how and when the UK leaves the EU - “it must be on or before 31 October and conceivably without a deal" - are too close to Johnson’s to offer a serious alternative.

So in practice Tory MPs have to pick between Hunt, Gove, Javid, Hancock and Stewart.

Javid, Hancock, Stewart, Gove and Hunt - could one of these really stop Johnson? Credit: PA

It is not an easy decision for them: Hunt may well be the best negotiator, which is relevant to those all-important Brexit talks, Gove knows Johnson's frailties and vulnerabilities better than anyone, Javid has the best story to tell about why he understands modern Britain, Hancock is the clever technocrat and then there is the Rory Stewart paradox.

He came in last place of the survivors with just 19 votes. He was barely known till he joined the cabinet as international development secretary a few weeks ago.

And, like Johnson, he is a white male posh public schoolboy, so not exactly redolent of modern Britain in all its sparkling diversity.

But Stewart has shown a magnificently intuitive grasp of how to use social media and the old-fashioned stump - and makes all his rivals, including Johnson, look painfully constipated.

He sees himself unashamedly as a stylistically Trumpish grandstander for the centre-ground of politics.

It is no stroke of luck that from nowhere he now has significant public recognition and may already be the second choice of Tory members, albeit trailing Johnson by a big margin.

So the safe choice for Tory MPs who want to give Johnson a bit of a test is Hunt or Gove. The high risk and potentially high rewards bet would be Stewart.

There is still - just - a game on.