It is very hard indeed to find a Conservative MP who can simultaneously look one in the eye and say that Theresa May should lead the Party into the next election.  Most agree with the plurality view expressed over the last year by our Members Panel: that she should quit, but not now.  Many Tory MPs believe that there should be a changing of the guard once Brexit takes place at the end of March next year.

Until now, that has also been the view of most of the members of the European Research Group.  The case put to them by Jacob Rees-Mogg and other leading members has persuaded: namely, that Brexiteers must focus on Brexit itself, and on helping to deliver the legislation that sets the legal framework without which it would be inoperable.

A confidence ballot would be a distraction from this mission, to put it mildly.  At a crucial juncture in the most important Government negotiation in modern times, the Tories would whistle up the self-indulgent carnival of a challenge.  If successful, it would remove the woman heading the British side of the talks, stall them at a moment when the Government needs more time rather than less, and plunge the ruling party into the bloody business of a leadership election.  If unsuccessful, it could reinforce Theresa May’s internal standing, thus empowering her to dilute a Chequers plan that already dilutes her previous position.  Either way, Rees-Mogg’s logic is sound.

Why is it, then, that – as Robert Peston reported yesterday – there was open discussion at yesterday evening’s ERG meeting of mounting a leadership challenge sooner rather than later.  The Daily Telegraph claims that “35 letters have now been submitted to [Graham Brady], just 13 short of the number of letters that would automatically trigger a vote under Party rules”.  We advise caution.  Only one person can know how many letters requesting a ballot the Chairman of the 1922 Committee has received – namely, Sir Graham himself.

But the fact of the debate at yesterday’s meeting is real enough.  ConservativeHome is told that some MPs have put in post-dated letters of no confidence and that, in at least one case, such a letter has been submitted with the request that it only be opened in the event of Sir Graham receiving 47 others – making it the one that tips the balance and triggers a ballot.  What, then, has changed in the week or so since Conservative MPs returned from their summer holidays?

There are three main factors.  First, it appears that the Prime Minister isn’t going to drop the Chequers scheme, at least before Party Conference, and it now seems possible that the EU will accept it as the basis for a deal – though the Commission and the EU27 will doubtless come back with demands over customs, services and immigration.  So some pro-Brexit MPs now argue that the only way of stopping Chequers is to depose May.

Second, Downing Street’s attempts to sell the scheme are meeting with mixed success.  Brexiteering MPs are being briefed, at dinners or elsewhere, by Gavin Barwell and Robbie Gibb.  But with all due respect to both gentlemen, most Tory MPs will want to have the case for Chequers put to them by a fellow MP and a senior pro-Brexit Minister: Dominic Raab, say; or Liam Fox and, above all, by the Prime Minister herself.  Where is she, our columnist Henry Newman, the Director of Open Europe, asked yesterday?  Where indeed?

Finally, the Brexit negotiation, May’s future and Boris Johnson’s ambitions are now all tangled up.  For all his impulsive private life, the latter is a calculating public operator: he withdrew his candidacy, remember, from the only Tory leadership election in which he has been a runner.  But his florid Telegraph columns, and stealing of the show yesterday at the launch of an ERG-backed paper, suggest that he knows that, as far as a Johnson premiership is concerned, it may be now or never.  That is certainly the take of some of his backers.

But if there is a mood among some Brexiteer MPs flows one way – i.e: towards a challenge, perhaps soon after Party Conference – there is also one among others that moves in the opposite direction.  The 80 or so MPs on the ERG’s mailing list are not a uniform band.  Not all of them are admirers of Johnson, or are resolved to oppose Chequers – that’s to say, to vote down an EU withdrawal settlement and whatever vague political declaration accompanies it.  Furthermore, not all pro-Brexit Conservative MPs are ERG members in any event.  We counted 129 Tory MPs as Leave supporters at the referendum.  That means that at least 50 who backed Brexit aren’t signed up to the ERG.

On the one hand, order near the top of Government is fragile.  Even the Cabinet Ministers who keep faith with Chequers do so on their own terms.  (Jeremy Hunt’s defence of the plan last weekend could be read as a warning against concessions on freedom of movement.)  Above all, the Prime Minister has failed to explain why she ditched the mutual recognition approach set at Mansion House.

But on the other, discipline and coherence among Brexiteers themselves, so marked during the passage of the withdrawal legislation, shows signs of strain.  There is a coherent Canada Plus Plus Plus alternative to Chequers, set out in the Alternative White Paper drawn up by David Davis as Brexit Secretary, and published on this site.

And today, Davis, Owen Paterson, Theresa Villiers and David Trimble will launch an ERG paper on how the Government should handle the UK-Ireland border, which is welcome.  None the less, some pro-Brexit MPs have been less disciplined than they might be.  Yesterday’s launch of an Economists for Brexit paper should have been left to the platform speakers, rather than become a bit of a free-for-all.

The ERG leadership put a prompt stop to trouble-inviting proposals from Brexiteer MPs for post-No Deal star wars systems and Falklands expeditionary forces.  We mean no offence to Conservative MPs when we say that not all of them are front-rank operators outside their constituencies and the Commons – that’s to say, at crafting and executing a political strategy.

But the main problem for pro-Brexit MPs is neither the lack of an alternative to Chequers (there is one) nor the distintegration of discipline.  It is, rather, that many are wrestling with the same question that we keep putting.  If the Commons votes down a deal based on Chequers, could the consequence be an unmanageable No Deal, or even no Brexit at all?

Whatever one’s answer, the case against a leadership challenge is no less strong this September than it was in July.  One can change the Prime Minister; but one can’t change the Commons, and the obstacles that a new Tory leader would face – at least, not without an election.  And after the experience of June last year, there is no appetite for risking marginal seats against a Marxist opposition.

Expect a backlash today against talk of a leadership putsch.  It usually comes to nothing: after all, there has only been one confidence vote in a Tory leader in over 15 years.  But keep your eye on events.  Sometimes they create their own momentum – as in the film, when you suddenly realise that the Sundance Kid, who can’t swim, is going to hurl himself off the cliff and into the waters after all.