Frank Dobson was sounded out about standing shortly after the 1997 election; more recently, Mo Mowlam was put in the frame. Neither would do the decent thing - although their arms, or that of the environment minister Nick Raynsford, may be twisted again in the autumn. But even if a heavyweight is found to beat Ken Livingstone, the left winger is still threatening to stand as an independent. Millbank has postponed the choice of candidate until after the party conference in an attempt to avoid a row.
William Hague is not doing much better at finding a Conservative candidate he feels proud of - Tory party members will vote on their choice in October. The business lobby group London First is calling for the race to be a battle of ideas not personalities. But, with only nine months to go until five million Londoners go to the polls, and six candidates already showing their hands, it is already turning into a highly personal campaign.
Credentials: The millionaire novelist and former Tory party deputy chairman says he is "vulgar - just like a mayor should be". From his collection of Warhol paintings to his penthouse overlooking the Thames and his inveterate name-dropping, he cannot help being ostentatious. But he has been campaigning longest of all the candidates, with a team of advisers already working flat out.
Image: Cheeky chappie populist - though his weakness for "inaccurate precis", as his wife Mary calls it, may earn him a battering.
Manifesto: Free milk and muesli bar for every child. Express bus system carrying passengers on 15 radial routes from the suburbs into the city centre for pounds 1. Streets to be tidied by a Commissioner for Dirt, helped by an army of young offenders forced to remove graffiti. Lord Archer wants to change the system of summertime so that London stays lighter at night. The plans would be funded by taxing the utilities companies every time they dig up the road.
Credentials: The millionaire car dealer has wide experience of the capital's traffic problems - as a Tory transport minister he advocated travelling by car in order to avoid the "dreadful human beings" who sit on the bus; later, as director of the Road Haulage Association, he brought Park Lane to a standstill by masterminding demonstrations of lorry drivers.
Image: Love rat. He is most famous for being the minister who had five mistresses.
Manifesto: He has pledged to stop public transport fares rising above inflation, to introduce modern, faster ticketing procedures and "remove the trade union stranglehold on London Transport". London would become a "24-hour city" with shops and restaurants open around the clock, and the capital would be put through an "architectural revolution" to enhance its skyline. Tackling crime would also be a priority, with the police ordered to "switch their efforts from grabbing headlines to catching muggers, car thieves and burglars".
Credentials: As a former leader of the GLC, Red Ken has already run London once, in the early 1980s. He became a hate figure for the tabloids who fingered the same "loony left" policies that are likely to be highlighted by New Labour as the campaign hots up. His chances of victory will be increased, however, by the perception that the "control freaks" at Millbank are trying to prevent it.
Image: Popular left winger, also famous for collecting newts. A political outsider: "Anyone who enjoys the House of Commons," he once said, "probably needs psychiatric care."
Manifesto: The creator of the GLC's "fare's fair" transport policy has promised to freeze tube and bus fares for four years, while introducing two new taxes on drivers. His deputy mayor would be made chairman of the new Police Authority and asked to examine "zero tolerance" crime-prevention regimes like those in New York. And he wants to build the biggest aquarium in the world in London (specialising in newts).
Credentials: The black television presenter says he has "pounded the streets" of London as a campaigning journalist and seen the problems of congestion, pollution and poverty. As the only ethnic minority candidate, he is well placed to appeal to the large black and Asian populations. Peter Mandelson was his best man - both a blessing and a curse in trying to win the support of Labour Party activists.
Image: He boasts that he is a "true cockney", but he is more of an Islington man. He angered some Labour activists by sending his two daughters to private school.
Manifesto: Trafalgar Square and Parliament Square to be pedestrianised. Parents would be encouraged to walk their children to school on child- friendly "school routes". These, like the rest of the capital, would be monitored by a network of closed-circuit television cameras. He wants to turn London into the "most wired city on earth" with every home linked up to the internet, and shops and bars open 24 hours a day.
Credentials: Her time as a transport minister may have taught her a great deal about the problems of the London Underground, but the main boost to her campaign will come from the Oscars she won as an actress. Her starring roles in films such as Women In Love make her a high-profile populist candidate - even though she hates the trappings of fame.
Image: Despite her glittering career on the screen, she is avowedly puritanical, drinking mineral water and avoiding make-up as much as possible. Her critics complain that she lacks charm and is too wooden to win over the majority of Londoners.
Manifesto: Ideas to be published in the coming month. Aides say her proposals will focus on tackling the capital's social problems, including poverty and homelessness. She has said she wants to "unlock the potential" of every Londoner. John Prescott and Gordon Brown are said to have thrown their weight behind her campaign.
Credentials: He grew up in Brixton and went on to become chairman of the GLC before going into Parliament. Has earned some credibility since being sports minister and will continue to enhance his reputation by handling Britain's bid for the 2006 World Cup, but he remains the court jester of politics. He once compared William Hague to a "foetus", publicly crossed his fingers while swearing the MP's oath of allegiance to the Queen, and then said he was "gobsmacked" to be made a minister.
Image: Witty, Armani-clad, champagne-swilling left winger. Downing Street knows he would be a colourful but decidedly unsafe pair of hands.
Manifesto: Still unclear what he would stand for, but he's never stuck for words. As an animal lover, he made no bones about calling the Canadians "dickheads" over their policy of seal-culling. Mr Banks may no longer be sports minister but he remains a keen fan, and he could well make better sports facilities for London a key aim.