(CNN) -- The International Olympic Committee was preparing Friday to elect a host city for the 2016 Summer Olympic Games. It's a prize so sought-after that presidents, sports legends and royalty have turned out to lobby for their country's city.
Four cities on four continents are in the running as IOC members gather in Denmark. Each city will have about an hour to make a final presentation and answer questions before the voting begins Friday evening.
The U.S. city of Chicago would have been the front-runner on merits alone, even if U.S. President Barack Obama hadn't come to Copenhagen to push for his hometown, experts said.
The presence of Obama -- the first U.S. president to attend an IOC vote -- is the talk of the town. His wife, first lady Michelle Obama, is also in Copenhagen to lobby for Chicago and has promised, half jokingly, that the "gloves are off."
Also in the running to host the two-week sporting spectacle: Tokyo, Japan; Rio de Janeiro, Brazil; and Madrid, Spain. Each will make its presentation in an order determined by the drawing of numbers.
All four cities have already had more than a year in the spotlight. They were whittled down from seven possible contenders in June 2008 and have been fiercely promoting their bids ever since.
After the cities make their presentations, the IOC members will sit down to cast their votes in a secret ballot. Ninety-seven of the IOC's 106 members are eligible to vote in the first round; seven must sit out that round because they represent one of the countries bidding for the Games. One other member is currently suspended, and IOC President Jacques Rogge has chosen not to vote.
A city must receive a majority of votes in order to win. If no city receives a majority, voting moves on to a second round, with the city receiving the lowest number of votes being eliminated, an IOC spokeswoman said.
Not to be outdone, Spain's King Juan Carlos and Queen Sofia and Spanish President Jose Luis Rodriguez Zapatero are planning to push the case for Madrid, according to the Madrid 2016 bid committee.
Brazilian President Luiz Inacio Lula da Silva and soccer legend Pele were expected to join forces to advertise the benefits of a Rio Games.
And Japanese Prime Minister Yukio Hatoyama, just two weeks into the job, also planned to be at the vote to demonstrate the government's full backing of the Tokyo bid, the bid committee said.
The presence of Obama -- who was born in Hawaii but spent much of his life in Chicago -- may give that city the crucial votes it needs if the margins are slim, experts said.
"I think it's going to be important enough to change the opinions of some IOC members," Hula said. "And if this is a close race, a few votes in favor of Chicago could be decisive."