When I hear the word charisma, I reach for my pistol. I am not even sure what it means, but I mistrust it, especially in a politician, because if you have it, you can get away with anything. And whatever it is, Boris Johnson has it.

When you think of him, you will initially think of a bicycle. His most visible act as mayor of London has been to strew the city with bikes that say, "Barclays". He is very comfortable with moneylenders, allowing the payday lender Wonga, with its shameful 4,212% representative APR, to sponsor free travel on the underground on New Year's Eve. But the way in which he has done little has worked magically. He is now the most popular Conservative politician in Britain.

YouGov's latest figures show him polling at 39% to Ken Livingstone's 33%; nationally, the Tories are on 32% to Labour's 51%. It is predicted that one in five Labour voters will vote for the charisma to go on, and bring him victory next year. He will eventually, I'm sure, bid for Cameron's job; he refused to deny it in an interview in Prospect this week. And, if you agree with my theory that the British electorate will always vote for the candidate who most resembles Princess Diana, he will get it.

Johnson, the subject of a new biography by former colleague Sonia Purnell, is presented as a riddle wrapped in an enigma, under a wig. That he is not. He is simply a politician who can appear on Have I Got News For You and make better jokes than Ian Hislop, which is not as remarkable as it sounds. Johnson is, at heart, a star journalist, a hack, a show-off. Sometimes I wonder if his entire political career is a stunt feature – Boris in China! Boris in Clapham! Boris on a bike! The Boris-on-a-bike spiel irritates me, because he rather likes taxis. Mayoral expenditure on taxis rose from £729 in 2007/08 to £4,698 in 2008/09 and Johnson once spent £99.50 on a taxi from City Hall to Elephant & Castle, and back again. Perhaps the strangest thing about this story was his presence, however fleeting, in Elephant & Castle. He is also a gaffe merchant, who loves to taunt himself with the possibility of his own self-destruction. He is, in fact, more like Julie Burchill than Margaret Thatcher, although all three will be insulted by the comparison.

I read through the long list of Johnson gaffes – racism, homophobia, priapism, rudeness to the people of Liverpool. Of Tony Blair's trip to the Congo, he wrote: "No doubt the AK47s will fall silent and the pangas will stop their hacking of human flesh, and the tribal warriors will all break out in watermelon smiles to see the big white chief touch down in his big white British taxpayer-funded bird." Some will say this is not technically racism, because he places the words in the mouths of another – in propria persona. His comment, "it is said the Queen has come to love the Commonwealth, partly because it supplies her with regular cheering crowds of flag-waving piccaninnies" is a perfect example of in propria persona; and once you know it is in propria persona, is it so offensive? Even so, that is what he has to say about Congo.

And to homophobia. "It is more sensitive to spare parents' anxieties than to allow leftwing local authorities to waste taxpayers' money on idiotic and irrelevant homosexual instruction," he said about Section 28, which was repellent, even though I'm sure he wouldn't repeat it today. Perhaps he had an epiphany at Pride, but I doubt it. Empathy is something you learn young, or not at all. He smelled the wind, and knew it had changed.

What to say about the priapism? It is nothing to do with me, though to be a gossip columnist in the 1990s was to watch Johnson stare down women's dresses, and to see his wife's face change. I am sure Mrs Johnson has her own way of dealing with this humiliation. I heard his entire salary flies into her bank account, which is brilliant, if true – Carmela Soprano's revenge. What concerns me is that he gets caught so often, he obviously wants to get caught. He is not yet Silvio Berlusconi, who once said: "According to a survey, when asked if they would like to have sex with me, 30% [of Italian women] said, 'Yes,' while the other 70% replied, 'What, again?'" But he has the potential.

Two thirds into a piece about Boris Johnson, and it reads like a gossip column, which is not his problem, but ours. So, to the facts. What has he done? By January, a single bus fare using an Oyster card will have risen by 56% from the time he was elected, and a weekly zone 1-4 Travelcard by 23%, costing passengers £416 a year more. This might bother a man with more empathy, but Johnson called his £250,000 a year for his Daily Telegraph column, "chicken feed," so he probably thinks £416 is a number too small to exist. Tube delays are up, as is crime, although it would be unfair to say he is personally responsible. The figures for August show that murder is up 3.1% on a rolling 12-month basis, residential burglary is up more than 7%, rape 10.4% and robbery against the person is up 15%.

This is not surprising, because despite his posturing over housing benefit, the cuts that he called "Kosovo-style ethnic cleansing," Johnson is an old-fashioned Tory. He did not stand up for the educational maintenance allowance or the childcare affordability scheme, or against tuition fees, despite London's vast student population. He has nothing to say on the NHS, not even a gag he can catastrophically misjudge, and grovel for. But he does oppose the 50p tax rate, obviously. He has called concern about bankers' behaviour "neo-socialist clap-trap", and the impact of annual bonuses on house prices, "whingeing". No wonder he cares for the bankers; he spends a lot of time with them.

According to his official diary, between May 2008 and March 2011 he held 86 meetings with bankers and the financial services industry representatives but only 48 meetings with the Metropolitan police. They, meanwhile, are being cut like ribbons. In July 2011 HM Inspectorate of Constabulary estimated the number who will be lost at 1,907 police officers, 920 community support officers and 374 staff. He also has no "ideological problem" with charging children to use playgrounds; in fact he appointed Eddie Lister, the head of Wandsworth council, who tried to pilot the idea, to be his chief of staff this year.

So, fewer police, more expensive and slower transport and a lot of happy taxi drivers and bankers. Labour voters who are considering voting for Boris Johnson would do well to check what he is actually doing and how good his judgment is. He called the phone-hacking scandal "codswallop cooked up by the Labour party", "spurious and political" and "a song and dance about nothing". Wrong on every count – when I think of him in the end, I think mostly of the time he helped the police raid a suspected drug dealer's flat. "What the fuck are you doing here?" said the man, when he saw the famous hair. I have to say, charisma aside, I agree.