Boris Johnson - labelled a right-wing buffoon or a breath of fresh air - has the Labour Party running scared. So scared that strategists have told the party to stop calling Boris, 'Boris'.

It was humanising him.

For all his buffoonery, Boris does indeed seem more human than the increasingly crusty, but once 'cuddly' incumbent, Ken Livingstone. And Mr Johnson is polling up to 10 points in front.

Ken has two weak points: crime and personality. Both seem unjust. Despite lurid headlines after every fatal stabbing, most crime is down, partly due to his extra police officers. Ken is lauded on nearly all major issues: his congestion charge is liked; his taxing of 4x4s popular; his public transport improvements applauded; his delivery of the 2012 Olympics appreciated.

Yet Ken, the heavyweight, looks down and out, outpaced by a lightweight challenger.

Why? Because the mayoral election is not fought on issues. Tony Travers, director of the Greater London group at the London School of Economics, told the Evening Standard that after eight years Londoners want a change, not least from Mr Livingstone's personality.

Ken is no longer the populist renegade who won the 2000 poll as an independent, says Professor Travers. 'He is seen as arrogant, angry and tired.'

Mr Livingstone's aura rankles, too, giving the impression that he holds a divine right to office, says Professor Travers, and he reverts to tired tirades when attacked.

Accusations of cronyism have stung as have claims of his indifference to overspending. Although last week he was cleared of improper political donations, the mud stuck.

Last week, it was revealed that he had five children with three women. He brushed it off in trademark style: 'As long as you don't involve children, animals and vegetables, Londoners leave people to live their own life in their own way.'

Boris cannily buried his past a day after, admitting to cocaine and cannabis use at Oxford University. Few Londoners batted an eyelid.

A panel concluded that Ken should focus on presenting himself as the competent CEO who regards Boris as a clown and a fake, offer key jobs to rivals and that the best way for Labour to help is to stay away.

The Observer's Andrew Rawnsley warns Boris has been muzzled from his 'gaffe-prone self' by Australian right-wing campaign boss Lynton Crosby and blanketed by Tory leader David Cameron's advisers.

But he has to slip up sometime, a prospect Tories fear will happen after he has become mayor but just before the party starts to fight a general election. Boris may become a bad taste of things to come.

'Have you ever seen Boris's room at the House of Commons?' a worried Tory told Rawnsley. Apparently it's 'a smelly anarchy of papers and gym shoes'.

Rawnsley says Ken must try to convince the capital it is better to stick with the old devil you know, than risk a clowning chancer they don't know until it is too late.

Tomorrow: Sydney