UK 3 September 2018 Theresa May has a numbers problem on Brexit. But Boris Johnson’s is bigger The former foreign secretary’s campaign to bin Chequers has enough supporters to succeed, but not necessarily enough to oust May – or elect him. Getty Don’t Bet On It Sign UpGet the New Statesman's Morning Call email. Sign-up “Theresa May’s Brexit problem isn’t Boris Johnson. It’s maths.” I was reminded of this line by Stephen Bush from last week, when I saw that the former foreign secretary had chosen to kick off the new parliamentary term with another attack on the Prime Minister’s Brexit plan in his Telegraph column. The hard-core of Tory Leavers are resolved to kill off Chequers over the coming weeks, and Johnson is their figurehead. That campaign is now doubling as his leadership bid. But only one of them is likely to be successful. Johnson, like Theresa May, has a maths problem. His is just as acute. On the one hand, we already know that there are more than enough Conservative MPs to vote down May’s Brexit plan. Only seven are needed to do so. That the Leavers will have no problem marshalling many more than that is illustrated by today’s Times splash: 20 have now committed publicly to forcing May to rip up Chequers. They could eventually number 60 or more. Therein lies Johnson’s maths problem. While there are enough MPs to scupper the Prime Minister’s Brexit plans, it doesn’t necessarily follow that there are 159 MPs who would be willing to vote against May in a confidence vote. Even if we suppose there are, there is no chance that all of them would break for Johnson in the ensuing leadership contest; nor is there any certainty that he would have enough supporters to reach the final round and his adoring fans in the membership. As far as his leadership ambitions go, Johnson’s maths problem could be fatal. There are enough MPs to dump Chequers, but are there enough to oust May and instal him? With every hurdle he passes, the number he needs to meet gets bigger, and the chances of him doing so get smaller. David Davis sums up his essential challenge well. “It is absolutely possible to dump Chequers without changing leader — and that’s the best way to do it,” he tells the Times. “Anyone who conflates getting rid of Chequers with changing the leadership is confusing their aims.” He might not be sincere when he says that. But for Johnson, it is precisely the problem. › Bob Kerslake: the housing crisis could turn into social unrest 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!