LONDON — The incumbent buys London’s bus fuel from the Venezuelan president, Hugo Chavez, and raises newts for fun. The challenger is a conservative product of England’s snootiest schools who has made a career out of wit and a startling squall of white-blond hair.

Both use language with the artful lethality of Muhammad Ali’s fists, yet each has a remarkable knack for sticking his foot in his mouth.

And if London voters can’t decide between Mayor Ken Livingstone and challenger Boris Johnson in the May 1 election for the city’s top office, they can always opt for Brian Paddick, a gay former police commander whose chief campaign supporter is Elton John. While the presidential primaries are providing the best campaign theater in years in America, London is abuzz with its own political spectacle.

“There has never been anything quite like this,” a specialist in London politics at the London School of Economics, Tony Travers, said . “It is quite a colorful election, particularly given the downright oddity of the main candidates.”

The race is ostensibly about crime and transportation woes, preparations for the 2012 Summer Olympics, and strategies to fight climate change — including Mr. Livingstone’s plan to slap a $50-a-day fee on any SUV that enters the city center.

But the real issue in the race is the men themselves, as their outsized and often outrageous personalities dish Tabasco sauce into the bland milky tea of British local politics.

With six weeks to go, polls, pundits, and bookies agree that the contest is neck-and-neck between gritty Mr. Livingstone and witty Mr. Johnson, with movie-star handsome Mr. Paddick giving sly Greek chorus-style commentary from the spotlight’s edge.

“I feel like I’ve just been machine-gunned,” Mr. Paddick said to laughter at a recent debate, after Mr. Johnson recited a rapid-fire list of policy proposals in his mouth-full-of-marbles, upper-crust baritone.

Later in the debate, an audience member in her early 20s complained that she felt unsafe at her local bus stop. Mr. Livingstone shot back that bus travel is far safer than when he took office, and that if she didn’t see that, “I don’t know what you’re on.”

In an interview, Mr. Paddick said Mr. Livingstone’s treatment of the young woman was “inappropriately aggressive” and showed the mayor’s habit of “lashing out indiscriminately at anyone who dares cast any doubt on his record.”

“Ken keeps newts,” Mr. Paddick deadpanned. “And a little-known fact about newts is that when they’re under threat from predators, they become poisonous.”

At their recent debate, Mr. Livingstone was rattling off statistics about his environmental record when Mr. Johnson kept cutting off a man he calls “Mayor Leavingsoon.”

“I would have thought at Eton they would have taught you not to interrupt other people,” Mr. Livingstone said, poking fun at Mr. Johnson’s elite Eton School and Oxford University pedigree. “You get that for free at most schools.” In an interview later, Mr. Johnson thrust back at the man long known as “Red Ken,” who once described Fidel Castro’s communist revolution in Cuba as “one of the high points of the 20th century.” “He used to be a red-hot lefty, and he wants to show he’s still got a little of the Che Guevara fire in him,” Mr. Johnson said. “But I think he’s very stale.”

Messrs. Livingstone and Johnson have strong supporters, but in numerous interviews across the city, many Londoners tended to be passionately against — rather than for — one of them.

“Ken Livingstone is rubbish,” Charlie Ryall, 21, a wine merchant, said. “I just think that he’s a greedy little horrible man.”

Said banker Umesh Patel, 36, “If it was a chimp and Livingstone, I’d probably vote for the chimp.” A bookseller and musician, Andrea Ughetto, 37, said she preferred Mr. Livingstone because Mr. Johnson is a “fascist” and “a very privileged man who wants very few people to be privileged.” Mr. Johnson, 43, is a longtime journalist for the Daily Telegraph and a former editor of the Spectator magazine, two of Britain’s leading conservative publications. In print and on television, and as a Conservative Party member of Parliament since 2001, he has earned a reputation as a megasyllabic merry prankster.

He putters around London like a rumpled polar bear in wrinkled expensive suits and a tie flopping here and there, often on a bicycle. With his unique head of hair, Mr. Travers said, Mr. Johnson is “one of the few politicians in the world you can recognize from the back.” Mr. Livingstone, 62, the acid-tongued rebel from the Labor Party, has been in politics since the 1970s and was elected London’s first mayor when the position was created in 2000. He has the wiry build of a mountaineer, slight but potent, with deep creases at the corners of his piercing and skeptical eyes. He is widely credited with engineering London’s successful Olympic bid and working with London’s high-flying capitalists to create a global financial hub that rivals New York.