London Mayor Boris Johnson cheers on the athletes on Day 8 of the Olympic Games on Aug. 4, 2012. (Alexander Hassenstein/GETTY IMAGES)

Look! Up in the sky! It’s a bird. It’s a plane. No, it’s Boris Johnson, unable to traverse a zip line in a single bound.

Sixteen-year-old Ye Shiwen may have mystified the world with her record-breaking swim in the 400-meter race. But the mayor of London’s YouTube moment — getting stuck on a line as he attempted to soar over Olympic celebrators, only to end up drolly calling for someone to “get me a ladder” — underscored one of the truly stunning accomplishments of the London Games: Bozza (as he is known here) has gone global.

Suddenly, the mop-topped mayor’s special brand of slapstick politics is no longer London’s little secret. Johnson’s antics have become the comic relief of U.S. Olympic coverage on NBC. The Russian press collectively rolled its eyes as he challenged President Vladimir Putin to strip “to the waist” for a judo match. France 24 declared his high-wire high jinks the Olympic “moment of indignity.” Johnson has not so much become the breakout star of these Games as its court jester.

But his antics, observers say, belie deathly serious political ambition. Political insiders call Johnson the clown who would be prime minister, a lion of the Conservative Party who has deftly leveraged Britain’s overdeveloped funny bone to become the second-most-powerful man in the country behind Prime Minister David Cameron, a fellow Conservative.

Much of Britain is guessing whether Johnson will stage his own bid for political gold at No. 10 Downing Street. His comedic turn at the Olympics has seen his popularity numbers in some polls soar, with the mayor of Western Europe’s largest metropolis finding comforting comparisons over the past week not just to John Cleese and Rowan Atkinson, but also Winston Churchill and Ronald Reagan. Raising speculation, Johnson is preparing a series of overseas visits after the Olympics that some here see as an attempt to portray himself as a global statesman.

Publicly, Johnson denies that he has ambitions to become prime minister — a job that under British law would be technically difficult for him to achieve while still serving as mayor. He shrugs off the question with evasive, if characteristically amusing, answers, such as the one he recently gave David Letterman when asked whether he had a shot at becoming Britain’s next leader: I have “about as much chance as being reincarnated as an olive.” (Letterman retorted: “Do you think the hair is holding you back?”)

But Conservative Party watchers increasingly think that Johnson does protest too much. They suggest that the 48-year-old mayor will be gauging Cameron’s weakness ahead of the 2015 elections and could potentially orchestrate a bid to unseat him if he deems his chances of success high enough. If he does, analysts say, historians could look back at the London Games as the tipping point for Bozza.

“The Tory Party can be a harsh thing,” said Tim Montgomerie, the influential British pundit, using the nickname of the Conservatives in Britain. “They got rid of Margaret Thatcher, and they’d certainly get rid of Cameron if it seemed to suit purposes. Boris is supposed to have a questionable private life and all the rest of it, but in difficult times, as we have now, sometimes you need big personalities. I think Britain may need one now.”

In the spotlight

To be sure, Johnson, born in New York to parents who spirited him back across the Atlantic as a child, has long played the card in a nation where a wicked sense of humor is often viewed as part of one’s intellectual bona fides. But even his close followers say he has outdone himself during the Olympic Games, relegating Cameron to an afterthought as Britain basks in its glorious moment.

Johnson was working these Games before they even began, seizing on a visiting Mitt Romney’s unfortunate suggestion ahead of the Opening Ceremonies that Britain lacked both Olympic spirit and readiness. Before a crowd of thousands gathered at London’s Hyde Park, Johnson mercilessly skewered the presumptive Republican presidential nominee, a fellow conservative.

The mayor’s acerbic wit found him later saying he “blubbered” at the Opening Ceremonies “like Andy Murray,” the Scot who suffered a tearful breakdown last month after losing in the finals at Wimbledon. Boasting of British athletes’ prospects at the Games, Johnson predicted “there are going to be more gold, silver and bronze medals than we’d need to bail out Greece and Spain together.”

Marveling at his potential rival’s uncanny ability to capitalize even on the most ridiculous of mishaps, Cameron last week quipped: “If any other politician anywhere in the world gets stuck on a zip wire, it would, you know, be disastrous. But for Boris, it is an absolute triumph. He defies all forms of gravity.”

There is no doubting that Britain, land of Monty Python, Absolutely Fabulous and Little Britain, likes a good laugh. But even here, there are some doubts about whether this nation would, if push came to shove, put such a funny man in No. 10 Downing Street.

And it is no secret here that Bozza has baggage.

Fired from as his first job as a journalist at the Times of London for fabricating a quote, Johnson nevertheless rose through the ranks, becoming editor at the conservative magazine the Spectator before winning a seat in Parliament. His reported extramarital affair became immortalized in a London play called “Who’s the Daddy,” and his alleged lying about it cost Johnson his job as the Conservative Party’s top official on the arts in 2004.

Johnson suffers from a chronic lack of tact, but his eccentricity could make him an exceedingly interesting statesman. He once referred to the Conservative Party’s tendency to destroy its leaders as “Papua New Guinea-style orgies of cannibalism” and criticized the entire city of Liverpool for “wallowing” in “victim status” after the 2004 kidnapping and murder of a Merseyside engineer in Iraq.

Is he electable?

Among Conservative loyalists, Johnson — an unabashed friend of bankers and the rich at time when neither are seen as political winners — is viewed as more true to the party’s roots than the moderate Cameron. In 2001, and before he beat “Red Ken” Livingstone for the London mayor’s job in 2008, Johnson questioned same-sex unions by wondering whether marriage between “three men and a dog” would be equally acceptable. As Cameron has embraced the cause of same-sex marriage, however, Johnson has also appeared to do an about-face. This year, for instance, Johnson banned a Christian group’s anti-gay ad campaign from running across London only weeks before his successful reelection in May.

Under British law, Johnson must first win a seat in Parliament before challenging Cameron as party leader and thus pave the way for a premiership. Yet, Bozza watchers say, a bid to ditch the London mayor’s job too early, or a move to hold onto it even as he seeks a national seat, could generate a voter backlash in London that would be hard to laugh off. It could also fuel his critics, who dismiss Johnson as an attention-seeking media hog who is heavy on personality but light on policy.

“The big question is whether he really is electable, or whether Britain would see a move by him to leave the mayor’s job as nothing more than a naked move for advancement,” said Sonia Purnell, author of “Just Boris: A Tale of Blond Ambition.”

Karla Adam contributed to this report.