Copenhagen:
The International Olympic Committee is familiar with tough decisions. It gambled by giving the games to Beijing and even turned down New York after 9/11.
But the race to host the 2016 games -- pitting Chicago, Rio de Janeiro, Tokyo and Madrid -- is still too close to call. Which means committee members will spend the next two days feeling like the most popular people on the planet.
Want to meet Michelle Obama? If you're on the committee and need a little pointer on which way to vote, it's not a problem. For added star power, the king of Spain, the president of Brazil and Oprah Winfrey have descended on Copenhagen.
Mrs. Obama, beating her husband to the Danish capital Wednesday, has a two-room suite in the IOC hotel, with cushy white leather furniture and an interactive table that, at the touch of a hand, shows how a Chicago Olympics might look.
The First Lady went straight to work impressing the IOC, with plenty of attention to detail. To committee member Nicole Hoevertsz, appointed a day earlier as permanent secretary of Aruba's Council of Ministers, she offered congratulations on the new job.
"We're not taking anything for granted, so I'm going to go talk to some voters," she said.
IOC members who have been through this selection process repeatedly, previously sending the games to London, Beijing, Athens and Sydney, say they could not remember a tougher choice.
With all four cities seen as capable -- at least technically -- of holding the Olympics, they said much rides on how the cities make their case in final 45-minute presentations to the IOC on Friday, before the vote.
"I have two favorites," Hoevertsz said. "It's going to come down to the last, last presentation. It's going to come down to the last minute."
And Mrs. Obama's mention of her new post in Aruba? "That was a very nice detail."
As time drew short, so did tempers. Despite fresh IOC warnings that the cities should avoid criticizing their rivals, the Spanish Olympic Committee's Vice-President, Jose Maria Odriozola, told the national Efe news agency that "Rio is the worst bid."
Rio bid organizers said the criticism was "totally unacceptable" and formally complained to the IOC.
The outcome on Friday could hinge on which cities are eliminated first in the IOC's secret ballot and how IOC members line up behind other candidates after their favorites are knocked out.
That makes predicting a winner perilous, and it means even IOC members who say they've made up their minds are still worth lobbying. There are 97 votes at stake in the first round, more in later rounds.
"It is difficult enough to know where the first-round votes are going to go, so trying to imagine where the swinging votes are going to go is impossible," said Spanish IOC member Juan Antonio Samaranch Jr, whose father was IOC president for 21 years.
"Events in the next 48 hours will decide the winner, because they will have a significant influence on the second- and third-round votes," he said.
Samaranch said he believes nearly all the IOC's voting members already have a favorite. But IOC Vice-President Chiharu Igaya said "many" are undecided.
Added British IOC member Craig Reedie: "This is really close. The closer it gets, the more people will say, let me think about it. We all want to see the presentations. It's what people see that will count. Decided? No, I haven't actually. I'm getting close."
Late, high-powered lobbying can be important -- as then-Prime Minister Tony Blair and his wife, Cherie, proved four years ago, when London campaigned successfully for the 2012 Olympics.
Blair traveled to Singapore ahead of the vote and spent two days lobbying members, inviting them to his hotel suite for one-on-one meetings. Chicago tore a leaf from his playbook: Obama adviser Valerie Jarrett met with Blair last week to get tips on navigating the IOC voting process.
But for the first time, there are no IOC executive board meetings in the days leading up to the vote. That means less opportunity for schmoozing.
IOC votes can be unpredictable. Aside from the paramount questions of whether bidding cities' Olympic plans are technically and financially feasible, emotion, sentiment, geography, politics, self-interest and other factors all play roles.
In Copenhagen, there's also the boldface-name factor, with Spain's King Juan Carlos and Brazilian President Luiz Inacio Lula da Silva already here and President Barack Obama jetting in for a few hours on Friday to bolster Chicago's presentation.
Willi Kaltschmitt, an IOC member since 1988, said the VIP presence would reassure voters that bids are fully backed by their governments -- but would be only one of many factors.
Australian IOC member Kevan Gosper said after meeting with Mrs. Obama, however, that she and her husband "could have an influence on marginal votes."
IOC members used to visit candidate cities themselves, but that was stopped because of concerns about bribery. Now they rely on IOC reports, presentations and lobbying to decide.
"Since we're not allowed to visit the cities, it comes down to the very, very little details," Hoevertsz said.
Ultimately, the choice may hinge on whether IOC members want to make a bold statement by sending the Olympics to South America for the first time or choose more familiar territory.
The United States, Spain and Japan have all previously held the Summer Games. Chicago could also be seen as a safer financial bet in tough economic times.
"One of the things that is very important to us now is the economic recession," said IOC member Nat Indrapana, adding that when cities made their cases to the IOC in June, "Chicago made a beautiful presentation."
When the voting begins, the city receiving the fewest votes will be eliminated after each round until one candidate secures a majority. The vote is expected to go the maximum three rounds.
IOC member Samih Moudallal said it will be like choosing among "four sons, or your brothers."
"How do you choose between your brothers?" Moudallal said, adding that he has yet to make his selection. "You have to use your mind and your heart together. It's a very difficult choice."