There's no need to bend the facts on buses, Boris

What's extraordinary is how self-inflicted it all is. As two of the Mayor's remaining aides appeared before the London Assembly yesterday, I continued to marvel at quite how badly Planet Ken is handling unaccustomed adversity.

At a meeting in Richmond, the Mayor, firing defiance, admitted no errors at all, continued to cry "racism", and vowed to reinstate Mr Jasper after the election. You have to win it first, Ken; and that promise, which has dismayed even your own supporters, made it just a little less likely that you will.

Despite the punishment he has already taken, Mr Livingstone still seems to be going out of his way to reinforce what has, I think, been the most damaging aspect of the whole business: his convincing impersonation of a man who does not believe he should be held to account; who responds, when questioned, with arrogance, untruths and abuse.

In clinging to Jasper for so long, the Mayor's image has moved from a charming straight-talker, parading his judgment as an election asset, into someone now looking both fairly nasty and faintly silly. If you want to show contempt for the voters, Ken, eight weeks before an election is not an especially good time.

Yesterday, too, Mr Livingstone actually tried, for the third or fourth occasion in the campaign, to turn the heat on Boris by bringing out the Darius Guppy horror. This was the phone call in which Mr Johnson was taperecorded agreeing to get the home address of a News of the World journalist, Stuart Collier, for his friend Guppy so he could be beaten up.

Does Ken remember what actually came of this call? Nothing. Collier's address was never supplied; the hack was never touched. More importantly, does Ken remember when this phone conversation took place? It took place in 1990, 18 years ago. Is he seriously trying to equate this with the Jasper scandal?

Yet for all the desperate, indeed comical, flailings of the Ken campaign, a time of danger for Boris may be about to begin. Sometimes, it's when your opponent is at his weakest that you have to be most careful.

One poll last week already had Johnson five points ahead. Now Jasper has resigned, Boris may well become the frontrunner - and if he does, that inevitably means that, to some extent, the media spotlight will turn away from Ken and onto him. Can he really be sure that his own platform will stand up to scrutiny?

Take the policy row of the week - Boris's pledge to replace the bendy bus with a new generation of conductor-operated Routemasters. This should have been a fairly open goal for Johnson. Not only is Planet Ken fighting Boris on one of his most popular policies, they cannot even decide how much to lie about it.

On 19 December, Ken's official reelection blog claimed it would cost £600 million a year to bring the Routemaster back. By 26 February, that figure had risen to £1 billion (almost twice the cost of the entire London bus network!) Just three days later, however, on a BBC phone-in, Ken's claimed cost of the Borismaster staged a dramatic collapse to £80 million, before rallying in late trading on Monday to £108 million. Could someone be making it up as they go along?

The problem, alas, for Boris is that he seems to be doing much the same thing. His price-tag (of £8 million, for the conductors only) ignores the need to staff a bus for three shifts. That takes you up to about £25 million. And what about the cost of buying the new Routemasters? They're a bit smaller than the bendies they replace, so you'd need about 20 per cent more (not three times as many, as Ken is claiming) for the same work. That probably makes another £100 million or so.

Ken's claimed figure is still an exaggeration, because the cost of the new buses would be spread over their whole 20-year service. And contrary to his propaganda, there is so much waste in TfL that fares are very unlikely to have to rise to pay for it. But on the Routemaster, the truth is that, possibly for the first time in history, a figure producedby Mr Livingstone might actuallybe more accurate than the alternatives.

At least the Routemaster policy is distinctive, along with a few other symbolic, small-bore things (traffic lights, for instance). But in many key areas, Boris is distinctly safety-first. I can imagine the John Humphrys question now: "Mr Johnson, you have made much of crime. But how exactly will your policy really differ from the Mayor's?" And I can imagine Boris struggling to answer. Will "personally chairing the Met Police Authority" and "replacing press officers with police officers", his two key pledges, change all that much?

Maybe nobody cares about policy. Certainly, few voters will examine manifestos in detail. But journalists and other politicians will. And as with the Jasper affair, the public will pick up the gist and texture from them. Many of Livingstone's claimed policy achievements fade badly when held up to the light. But could the same also apply to Boris's positions?

Luckily for Boris, all these questions have so far been largely drowned out by the ongoing Jasperama. I can promise more such entertainments in the future. I do also believe Johnson is a fundamentally more decent and honest person than Ken. In a personality contest, that's important.

But Boris cannot coast to power on the Evening Standard's coat-tails, or because of the awfulness of his opponent. More importantly, he does not deserve to.