UK 12 December 2018 Theresa May stakes her future on a promise she cannot keep: winning back the DUP The prime minister told the 1922 Committee that the only way of passing a Brexit deal would be with the DUP’s support - which they are unwilling to give. Getty MesseDUP Sign UpGet the New Statesman's Morning Call email. Sign-up Addressing the meeting of the 1922 Committee that will define her premiership - and Brexit - Theresa May made two seemingly impossible promises: not only would she win back her sometime allies in the DUP, but she would do so by wringing a legally binding promise on the Irish backstop from the EU. On one level, her doing so is a belated recognition of reality. If Labour MPs are unwilling to rebel in any significant numbers - which, as the past month has shown, they are not - then the prime minister cannot pass her Brexit deal is by securing the support of the 10 MPs who still, notionally at least, keep her power. May met Arlene Foster this afternoon and assured her MPs that good progress had been made and that things were on the mend. Her succeeding - both in this evening’s vote and in passing a deal - depends to a large extent on that being true. Square the DUP on the backstop and you square many Conservative Brexiteers too. Her senior ministers stressed this imperative. “She made absolutely clear that the only way of getting a deal is with the Democratic Unionist Party,” said one Cabinet member as MPs spilled out of Committee Room 14. Another, Liz Truss, confirmed she intended to do so by securing a “legally binding” assurance that the backstop is temporary. It’s clear - both from what the EU has said and what May did not say this evening - that said assurance is highly unlikely to come in the form of changes to the withdrawal agreement, which the European Commission and other member states will not entertain. As long as that is the case, it’s even clearer that the Prime Minister cannot make good on that first promise. In public and in private, the DUP have said that they will not accept anything less than substantive changes to the binding divorce deal itself, regardless of whatever bolt-ons May says she is confident the EU will agree to. Foster said as much after her meeting with May this afternoon, and her MPs are echoing the sentiment. They have made clear to those Tories who are hostile to May that, regardless of what the prime minister says, they have not been bought off. “No doubt we’ll consider what she has, but I can’t think how it would give the comfort needed without alteration to the text of the Withdrawal Agreement,” says one. That May seems to have concluded from her meeting with Foster that she is somehow closer to an accord has been met with exasperation but not surprise - the Prime Minister, after all, has proved herself pathologically incapable of taking the DUP at their very straightforward word. “I don’t think it’s a failure of interpretation. It’s a stubborn refusal to listen, all the while exhausting the time remaining to win suitable alteration.” Knowing that, it’s hard to escape the conclusion that May is staking her future - and that of an orderly, Westminster-approved Brexit - on a cheque that neither the DUP or EU are willing to cash. And that makes it very difficult to see how she can keep the even bolder promise with which she opened her speech: "There won't be a snap election." › Suspended Tory MPs are suddenly allowed to vote – while still facing sex offence claims Patrick Maguire was political correspondent at the New Statesman. Subscribe For daily analysis & more political coverage from Westminster and beyond subscribe for just £1 per month!