COPENHAGEN - Sport and politics converge in a potent mix on Friday with the credibility of the U.S. President on the line as International Olympic Committee (IOC) members choose the venue for the 2016 Summer Olympics.

The stakes could hardly be higher when more than 100 IOC members gather at Copenhagen's Bella Convention Center to choose between the rival bids of Chicago, Madrid, Rio de Janeiro and Tokyo.

Though the contest has long been regarded by most Olympic experts as the closest ever, with four potential winners in the field, there is no doubt that the Obama factor weighs heavily and has ensured Chicago takes the role of front-runner.

No incumbent U.S. President has ever addressed an IOC session before but Barack Obama has taken the boldest of risks to his political reputation by deciding to appear in person to back his home city campaign.

While he flies in overnight from Washington and goes straight into the IOC session, First Lady Michelle Obama will have been in the Danish capital for 48 hours, conducting a breathless series of one-on-one meetings with voting IOC members.

It is probably the biggest persuasion-by-charisma campaign ever undertaken in the Olympic movement.

The Obama factor may be Chicago's trump card but that does not mean the Windy City's three rivals are giving up the ghost.

Madrid claim by sending both King Juan Carlos and Spanish Prime Minister Jose Luis Zapatero they are actually trumping Obama.

Tokyo have newly elected Prime Minister Yukio Hatoyama flying in late on Thursday to join their bid team and Rio think they have charisma to spare by bringing in Brazilian President Luis Inacio Lula da Silva.

YES, WE CAN

In a news conference on Thursday, Lula cunningly took a leaf out of Obama's own electioneeering manual by using his Yes, we can rallying cry.

This time we look at the world and say yes we can, we can do it, he said, adding the country's 'magical' financial growth and relatively shallow recession made it the standout candidate.

London bookmakers have made Chicago the favorite with Rio the main challenger and Madrid the outsider behind Tokyo.

However, the Olympic selection procedure is almost notoriously unpredictable with members voting by secret ballot in a series of rounds until one candidate gets more than 50 percent.

In recent years, the front-runner has often come unstuck.

Beyond the personalities -- and the four candidates have all brought a clutch of sporting and cultural celebrities with them -- each bid has produced a technically strong plan of stadiums and infrastructure.
But each has its advantages and its handicaps in the eyes of the IOC.

Chicago would maximize sponsorship and TV rights revenues but has to live with the legacy of the 1996 Atlanta Games, the last Summer Olympics staged in the U.S. and generally regarded as this most disastrous with a host of organizational failures.

Rio would be the first South American city to stage the Games but has a horrendous crime rate it would rather forget and is already under the pressure of preparing for Brazil's 2014 Soccer World Cup.

Tokyo's state-of-the-art arenas and spectacular waterfront location are appealing but would the IOC want to return to the Far East so soon after last year's Beijing Games?

Madrid has a highly crafted bid which came agonizingly close to beating London for the 2012 Olympics but would have to persuade the IOC to stage the Games in Europe twice in a row.

However, the big question is with Obama, who would win all the kudos for success, as then British Prime Minister Tony Blair did for London four years ago and then Russian President Vladimir Putin did for the Black Sea resort of Sochi when it won the 2014 Winter Games two years ago.

If Chicago loses, Obama has one consolation. Nelson Mandela went to the IOC at its home base of Lausanne, Switzerland 12 years ago to back Cape Town's bid. The IOC was dazzled by his presence -- but Cape Town placed only fourth behind Athens.

(Additional reporting by Karolos Grohmann and Kevin Fylan in Copenhagen; Editing by John O'Brien)

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