“Some of our valued colleagues with tiny majorities in Brexit-supporting areas will be completely stuffed by this.” That was the verdict of Philip Davies, the arch-Leaver Tory MP for Shipley, on Theresa May’s plan.

The resignation of Ben Bradley, the MP for Mansfield, as vice chair of the Conservative Party, shows this anxiety is a very real one – and that it extends well beyond usual Eurosceptic suspects like Davis. (Bradley is a leave convert but not a particularly ideological one, while Maria Caulfield, another Tory vice chair and a former remainer, quit too.)

Bradley’s majority in Mansfield, the Nottinghamshire mining town which the Tories won for the first time ever last June, is just 1,507. 71 per cent of his constituents voted to Leave.

In a letter to May, he said he did not believe those two numbers could be reconciled with supporting the Chequers plan and warned that pursuing it would be tantamount to handing Jeremy Corbyn the keys to Downing Street.

What does it mean? The answer that will get you lots of retweets is “not a lot”. Fair enough: the government will not fall because of the resignation of Conservative vice chairman for youth. It nonetheless demonstrates that, as far as her internal authority is concerned, May is still deep in the woods without a safe passage out.

That an ambitious MP in a marginal like Mansfield is quitting should sound alarm bells. At the 1922 Committee last night, May sought to cow her party into submission by warning that rejection of her deal – or a leadership challenge – would hand power to Labour. The spectre of a 1997-style defeat was invoked by the government payroll as they sought to encourage loyalty.

Unfortunately for the prime minister, the Tory MPs most at risk of losing their seats agree that mishandling Brexit could precipitate a Labour landslide, but think the way to prevent that is by performing a handbrake turn away from her plan for a soft Brexit. It is hardly a ringing endorsement of Downing Street’s belief that leave-backing seats in the Midlands and North are its only remaining path to a majority.

With more resignations likely to follow, isn’t clear how the prime minister escapes. In his resignation letter Bradley cites his frustration with the Northern Ireland backstop plan – the mechanism by which the UK and EU have agreed to prevent a hard border through continued regulatory alignment – and questioned why it was being allowed to prevent Britain pursuing the truly independent trade policy Brexiteers craved.

May’s contradictory commitments to not introducing new border infrastructure and not having a border in the Irish Sea mean it has to. Leavers don’t have an alternative plan to May's soft Brexit, which save for abandoning one of her red lines is the only means of squaring that circle. But what they do have is the ability – and numbers – to force the prime minister to try.