Will Ken Livingstone make way for the British Obama?

London's next mayoral election is not until May 2012 but Ken Livingstone is already campaigning. Indeed, he's been campaigning ever since his successor Boris Johnson took his place in 2008. The spectre at Boris's feast, Ken is never far from City Hall, never far from a microphone, never unavailable for a soundbite.

It's not hard to guess why the two-times London mayor hankers after a third term. It was on his watch that London won the right to stage the 2012 Olympics. If he can retake the mayoralty from Johnson in May 2012, he'll have a good ten weeks' breathing space before the July 27 opening ceremony.

There are many in Labour's ranks who believe it is fitting that the man who won the Games for London - with a little help, of course, from Seb Coe, David Beckham and Tony Blair - should enjoy the fruits of his undoubted enthusiasm.

He has support from John Cruddas, the increasingly influential East London MP, and from the Brownites, to whom he has been assiduously loyal during his unending tribulations. And he continues to court trade union leaders who were a key part of his power base.

So, even though he would be hitting 70 by the end of his term, Livingstone looks like a shoo-in as the Labour candidate.

The man standing in his path is Boris Johnson. The Tory has established himself as a popular mayor and, whatever ridicule he may have received for his typically shambolic role in the Beijing closing ceremony, he has to be odds-on favourite to romp home for an Olympic-era second term. Indeed he's so far out in front he might even imagine pausing at the winning tape, Usain Bolt-style, to acknowledge the cheers of the crowd.

But while 2012 is closer than you think - just ask an Olympics contractor or organiser racing to get East London ready for the Games - three years, give or take a few weeks, is a very long time in politics. The current picture could change radically.

By May or June 2010, unless he's knocked over by a bendy bus, David Cameron will be prime minister. A year on - less, possibly - he is likely to have become one of the most unpopular prime ministers in modern history. It doesn't matter that pollsters are currently recording a desire for public service cuts rather than tax rises. The public will be thinking very differently by the time those cuts begin to bite.

Unless an economic miracle intervenes, Prime Minister Cameron and Chancellor Osborne will oversee a bloodbath in public service cuts.

The trickle-down - make that pour-down - effect will be something to behold. 'Soft' Labour voters now happily rubbishing Gordon Brown will again have a flag to rally around. By the end of 2011, the Tory government will be heading into mid-term having outraged many members of their new fanbase and re-energised Labour supporters.

And who will be a convenient whipping boy for the Tories' butchery? Step forward Boris Johnson. Londoners could really make him pay.

At which point all hell will break lose in