UK 14 February 2019 Is the DUP heading for a split with Tory Brexiteers? Theresa May's unionist allies voted to endorse Theresa May's Brexit strategy tonight - unlike the European Research Group. Getty Sign UpGet the New Statesman's Morning Call email. Sign-up One of Westminster’s most popular truisms is that unlocking the votes of the DUP means unlocking those of most Conservative Eurosceptics, and with it delivering a majority for Theresa May. Both the European Research Group and latterly Downing Street subscribe to that logic, which is why the prime minister agreed to demand compromise from the EU27 on the Irish backstop - something it has neither the desire nor political incentive to offer - after the last set of Brexit votes last month. But when asked to affirm that strategy this evening, the DUP and ERG diverged. May’s confidence and supply partners voted for the government motion, while most ERG MPs followed Jacob Rees-Mogg’s instruction to abstain on the grounds that to vote for the motion would be to implicitly reject the principle of a no-deal exit. That the ERG leadership did not follow the DUP’s lead on a question they have long insisted the unionists to be the ultimate authority on - the government’s approach to the backstop - appears to undermine the argument that the road to a reliable parliamentary majority on Brexit runs first through North Belfast and then, inevitably, through North East Somerset. Though the strategic priorities of the DUP and ERG have been aligned throughout the Brexit process at Westminster, they have never been identical. The DUP’s preference will always be for a deal that keeps the Conservative Party intact for the simple, self-interested reason that it will keep this parliament and the unprecedented leverage they enjoy within it alive. But faced with a choice between no-deal and a UK-wide soft Brexit, all but one of its MPs would, unlike the ERG, pick the latter. That inherent tension means that the direction each bloc of MPs will move in as the clock ticks down to 29 March is harder to predict than Downing Street might expect. The ERG are nonetheless relaxed. They believe that their whip to abstain made a government defeat inevitable and thus allowed the DUP, cynically, to vote safely with the government without hurting Brexiteer interests. “It’s sucking up to the favour dispensers,” a source says, “and having your cake and eating it.” If May is ever to assemble a reliable majority with her own MPs and the DUP, she will hope that they are right. › Theresa May’s defeat confirms that the only way to pass a Brexit deal is with Labour votes 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!