Why Cameron needs to tame the big beast Boris

If the PM could harness the qualities of London's Mayor he would. But a Tory defeat would actually suit Johnson

Not even an MP yet, Boris Johnson has been promoted to the top team: he, Osborne and David Cameron will be the faces of the Conservative election campaign (AP)

We know he's coming, a Labour MP told me after the 2005 election. He is like a hurricane over the horizon, coming this way. We just don’t know where or when he will make landfall.

All we know is that the destruction will be terrible. He was talking about Gordon Brown, the Inevitable Successor. Now Conservative MPs speak in similar terms about Boris Johnson.

Last week, Johnson was photographed in tunnels underneath London’s Victoria station with Chancellor George Osborne next to a Soviet-style banner proclaiming: “Long Term Economic Plan for London.” Not even an MP yet, Johnson has been promoted to the top team: he, Osborne and David Cameron will be the faces of the Tory election campaign. That campaign will be run by Lynton Crosby, the Australian consultant who ran Johnson’s two winning London Mayor campaigns, in 2008 and 2012 (although he also ran Michael Howard’s losing general election attempt in 2005).

Johnson is an opportunist playing a team sport. “Boris has been so well behaved,” says a source close to Cameron, who is said to be pleased and surprised. Johnson’s answer to that question two years ago about whether he wanted to be prime minister captures him perfectly. “If the ball came loose from the back of the scrum ...”, Johnson, the individualist pretending to be a team player, would be there to scoop up the ball and score. Cameron and Osborne are pretending to be team players, too. They are hugging Johnson close like the front row of the scrum. “Boris has finally understood that the Prime Minister is not his rival,” I am told. “So he’s stopped fighting him.” His rivals are Theresa May, Osborne and, further into the future, Sajid Javid. Meanwhile, they are all bound to Cameron by a common interest. They all need to be seen by the Tory tribe to be helping the team win.

That is awkward for Johnson, because his chances of becoming Conservative leader may never be as good as they are this year. He really needs Cameron to lose in May, because he would, I think, easily win the Tory leadership election afterwards. He is the only candidate who can convincingly claim to appeal to people who choose not to vote Tory this year. That will be almost the only thing that will matter to Tory MPs and party members after a defeat. Yes, there is the buffoonery, the refusal to take anything seriously (although, in fact, when there was a helicopter crash in Vauxhall, killing two, he was a model of dignity). But he is the only politician with net positive poll ratings: that trumps any doubts.

Cameron and Crosby need that magic for their election campaign. They need the tousled gee-whizz-crikey expostulations, the paradoxical communion with popular culture, the unworkable ambitious ideas. I was told the Prime Minister loved Johnson’s plan to build an underground high-speed railway between London and Manchester. It would be a maglev system, using magnetic levitation, a capsule in a tube that would take 18 minutes, like an enormous vacuum cleaner. “Completely crackers, not going to happen,” said one sceptic in No 10, but Cameron wants to bottle some of that visionary enthusiasm for his campaign.

If that campaign prevails, Johnson’s path to the top is less certain. If Cameron were to win, Johnson would get a big job. Most people assume he would make a mess of it, because he wasn’t a very good shadow junior minister, but I am not so sure. His record as Mayor may be thin but he hasn’t embarrassed himself. For all his reputation as a dilettante he works hard. When he was editor of The Spectator he put me in touch with people who had known Tony Blair in his gap year and tried to get me to write an article about Blair smoking dope. I told him that everyone insisted Blair never touched drugs, and that this was more interesting, in that milieu, than if he had. But Johnson was sure the story was otherwise. He kept pushing, suggesting new lines of inquiry. Boisterous, forceful and wrong: that sums him up.

But even if he is a brilliant minister, the longer he has to wait the worse his chances. In five years, other challengers could prove themselves. Javid is an obvious possibility but a tiny part of Johnson must have died when he heard Esther McVey, not yet in the Cabinet, asked if she wants to be prime minister, say: “If I had to do a yes or a no, I’ll be honest, I’ll say yes.” Even if he does succeed in 2020, and he will only be 55, he may have waited too long. The record of those prime ministers who had to wait – Anthony Eden, Gordon Brown – is not encouraging.

But Johnson is coming, come what may. The only thing we don’t know is how bad the destruction will be.

Twitter: @JohnRentoul