The curse of personality politics: We love Boris Johnson only because he's good at wooing us...

... while Ed Miliband seems unable to avoid our disdain

Charm offensive: Boris Johnson’s air of pantomime bluster may not always be enough (Getty)

One politician lays a wreath at an event to mark the centenary of the start of the First World War. Like all but one of the other grandees asked to do so, he is given no time to write something to go with it, and so instead is presented with a perfunctory note, attached by the organisers, that simply says who it is from, in a comically loopy script. Another politician specifically breaks his word to those who elected him by taking on another job at the same time, because his ambitions have come into conflict with his promise. Which one gets it in the neck?

There's no way of posing that question that disguises the fact that it's a trick. Even if you've missed the specific events of last week that I'm talking about, you know how it goes: it was Ed Miliband who failed to write a note of his own, and Boris Johnson who did the thing that he swore he wouldn't. And a day after Miliband was ridiculed and vilified over a piece of trivia, and told that it showed exactly why he couldn't cut it, Johnson was exalted as a future prime minister without regard for his broken promise.

This is not a party political point. There are showmen and yeomen on both sides, and no ideology has a monopoly on empty pledges. This concerns a longstanding complaint about our politics that has recently hardened into a truism, an observation so self-evident that we are told there is no point in complaining about it any more by those whose acceptance has grown into a tacit endorsement. Ed Miliband gaffed; Boris Johnson broke a promise. But the latter got away with it, and the former was punished, because gaffes matter more than misdemeanours. Style has triumphed over substance.

Actually, it's worse than that: we have reached a consensus that style is substance, and the only substance that counts. Ed Miliband's way of eating a bacon sandwich has a far greater effect on his electability than Boris Johnson's invention of a quote when working as a journalist, or his lie to Michael Howard, the then Tory leader, over an affair or even the affair itself. Indeed, for Boris, the accumulation of these transgressions – these scrapes, jams, pickles, these gross errors of judgement – has become an intrinsic part of his buccaneering charm, the very thing that sets him apart from the men in grey suits. When they are brought up, he takes on the charmingly wounded air of the Terry-Thomas rotter confronted with his colourful past. It's all nonsense, old thing, he blusters. And in any case, it happened such a long time ago!

Performance has always mattered, of course. Any politician making bungling presentational errors that chime with a more general sense of incompetence is bound to pay a price. Damian McBride, who as a former adviser to Gordon Brown knows what a minefield it can be, had a point when he wrote that the whole wreath episode was a cock-up, and damningly indicative of incompetence and dismay on team Miliband. In this telling, the Labour leader's recent speech, in which he tried to make a virtue of his failings as a salesman, has left his advisers paralysed with fear lest they be caught doing anything that seems to prioritise image over policy. And McBride is right. Politicians must operate in the world as it is if they wish to win, and a failure to contend with it adequately really matters.

This is fine as a narrow diagnosis of a political problem. Where it falls short is as a prescription for our response. It's one thing for political analysts to note these shortcomings, quite another for the rest of us to treat them with the sorrowful scorn that ought properly to be reserved for failings that have some kind of moral dimension. This is what has changed, I think: we talk about this stuff without even paying lip service to the idea that it's shallow to do so. Others fall for this presentational crap, we think: our interest in it is strictly as an index of more general competence, so it's fine. It's actually rather sophisticated. But if enough people engage with this sort of nonsense with such self-delusion, instead of humourlessly pointing out that it doesn't matter how Ed Miliband eats a sandwich, then it doesn't really matter how watertight their rationale is, they are still driving it to the centre of the debate, and driving out other things that should be there.

Like about 50 per cent of modern life, this process recalls Don DeLillo's novel, White Noise, which features a remarkable tourist attraction, The Most Photographed Barn in America, self-perpetuatingly notable only for how many people pay attention to it. "No one sees the barn," says Murray, an academic on a day trip. "What was the barn like before it was photographed?... We can't answer the question because we've read the signs, seen the people snapping the pictures. We can't get outside the aura. We're part of the aura."

Miliband and Johnson are the barns, and we're the aura: we love Johnson because he is good at making us love him, and we feel disdain for Miliband because he seems incapable of stopping it.

It's possible that we will see a heartening correction to this process. Miliband's seemingly ill-advised admission that he's hopeless with photo-ops may, against all the odds, inspire a new seriousness in the press and the public, and the Wallace-without-Gromit jokes may give way to a new judgement on his policies. The power of Johnson's bluster may wear thin as people begin to consider him in a position of real power and start to ask questions about his capacities as an executive – which, by the way, may very well be considerable.

Somehow, though, I doubt it. I think of Eddie Mair's interview with Johnson in March last year, well-known as one of the very few times that a media interrogator has brushed off the BoJo charm and paid scrupulous attention to his chequered past. "You're a nasty piece of work, aren't you?" asked Mair, a question so rude that Boris began to appear genuinely flustered, instead of the pantomime version of that state that he usually deploys. Taken to task on every one of the most troubling points on his CV, Johnson might as well have been waving a white flag by the interview's end. Perhaps, you felt, the power of his charm was not as bottomless as it might have seemed.

Not a chance. Four days later, the Evening Standard ran another story about Boris on their front page. "VOTERS SAY BORIS MUST LEAD TORIES", ran the headline, revealing that a new poll had shown the party's fortunes would be transformed should London's Mayor ascend to No 10. Mair's interview, Johnson said, had been "splendid". If anything, it turned out, the confrontation had made people like him more.