Boris Johnson has been described variously as a "clown" and a "formidable opponent" by his two main adversaries.
His newspaper columns and regular appearances on the TV show Have I Got News For You have made him one of the most recognisable figures at Westminster.
But the 43-year-old's high profile has been achieved at a price, with bad publicity over rumours of affairs and a series of gaffes.
He was forced to apologise after an editorial in The Spectator magazine, which he edited at the time, said the city of Liverpool "wallowed in victim status" in the wake of the killing of Iraq hostage Ken Bigley. He also said sorry to Papua New Guinea after linking the island state with "cannibalism and chief-killing".
And he was fired from his frontbench job by former boss Michael Howard for denying an extra-marital affair with Spectator colleague Petronella Wyatt.
But the close friend of Tory leader David Cameron has a habit of bouncing back from such setbacks. He won a cult following among students and the respect of many university and school leaders after becoming the Conservative's higher education spokesman.
When he stepped down from that post to take on the mayoral challenge, some commentators predicted his gaffe-prone nature would make him destined to lose.
Indeed, his Liberal Democrat opponent Brian Paddick said of him: "We need a serious ambassador for London to be our mayor - not a clown."
But Labour's Ken Livingstone never underestimated the threat. The Labour mayor described Mr Johnson as "the most formidable opponent I will face in my political career".
Since being chosen as the Tory candidate for London mayor, he has made transport one of his key policy areas, launching a ferocious assault on the capital's bendy buses and praising the old Routemasters.