LONDON (AFP)---The race to become London's next mayor is shaping up to be Britain's political highlight of the year, with a cast of colourful characters and a backdrop of corruption claims and controversy.
   

Incumbent Ken Livingstone is seeking re-election for a third straight four-year term but vying to topple him is Boris Johnson, another instantly recognisable -- and idiosyncratic -- figure in British politics.
   

Also in the frame are Brian Paddick, a former senior police officer who once said he saw the attraction of anarchy, and a militant campaigner who has protested dressed as a superhero for separated fathers' child access rights.
   

In all 13 candidates have so far expressed their intention to contest the May 1 poll, which will see the winner control the city's 11-billion-pound (22-billion-dollar) a year budget and oversee the run-up to the 2012 Olympics.
   

But the vote looks like being a two-horse race between the Labour Party's Livingstone and the Conservative Party's Johnson -- two of only a handful of British politicians to be so well-known they are called by their first names.
   

Blond-haired Boris has stolen a march on Ken, whose once fervently socialist views and outspoken opposition to Tory prime minister Margaret Thatcher's free-market reforms earned him the moniker "Red Ken" during the 1980s.
   

A YouGov poll for London's Evening Standard newspaper last week suggested Johnson had 49 percent public support, putting him on track to dethrone the man he calls "King Newt" because of his hobby of keeping amphibians.
   

Livingstone has become underdog at 12 points behind with the Liberal Democrats' Paddick the next nearest challenger on 12 percent.
   

The mayor's campaign launch last Tuesday at the Royal Festival Hall suggested he is taking Johnson's challenge seriously, as he admitted: "This will be the toughest political fight of my life."
   

The underlying message of Livingstone's campaign is that Johnson will wreck all that has been achieved in his eight years as the British capital's first directly-elected mayor and his vision of progress for the next four years.
   

Johnson, currently bookmakers' favourite, counters that Livingstone is old hat, has abused his position and that it is time for change -- a call increasingly voiced by his colleagues in parliament against the government.
   

On Wednesday, Livingstone joined forces with the Green Party's candidate, Sian Berry, saying they had "common cause" to fight Johnson's environmental credentials.
   

Tackling climate change has been a defining feature of Livingstone's time at City Hall with initiatives like the congestion charge road pricing scheme that sees drivers forced to pay eight pounds a day to enter central and west London.
   

With Johnson opposed to Livingstone's plan to charge drivers of "gas guzzling" sports utility vehicles 25 pounds a day to enter central London and other measures to tackle air pollution and congestion, Berry urged action.
   

She also accused Johnson of having "contempt" for London's diversity, making the ex-journalist's attacks on political correctness and past description of black children as "picaninnies" with "water melon smiles" a campaign issue.
 

The man who has described himself as a "one man melting pot" -- he claims to be descended from a Russian slave while his great grandfather was briefly interior minister in the last Ottoman Turk government -- has since apologised.
   

He claimed the remarks, in a newspaper article six years ago, were taken out of context.

Livingtsone's controversies  

Livingstone, though, is not immune from controversy.

He was rapped for comparing a young Jewish newspaper reporter from the Evening Standard -- where there is a long-standing mutual loathing -- to a Nazi concentration camp guard in 2005.
   

And in recent months, the Standard has exposed alleged financial irregularities said to involve close aides of the mayor.
   

But on the sidelines, Tony Travers, a local government expert at the London School of Economics, thinks the high-profile spat can only be a good thing for democracy.
   

"Turnout should increase with a real contest between two well-known candidates. The 2008 London mayoral election will go to the wire," he wrote in the Evening Standard.