(CNN) -- As Rio de Janeiro celebrated the decision to award it the 2016 Summer Olympic Games, pre-vote frontrunner Chicago was in a state of shock as it was the first of the contenders to be eliminated, despite some influential backing.
The International Olympic Committee had gathered at Denmark's modern Bella Center convention hall in Copenhagen to hear the bids from Rio, Chicago, Tokyo and Madrid.
Chicago was widely seen as favorite, even without U.S. President Barack Obama's late appearance in the Danish city to sell his hometown.
But his presence -- he was the first U.S. president to attend an IOC vote -- was the talk of the town. His wife, first lady Michelle Obama, promised, half jokingly, that the "gloves were off" ahead of the vote.
It just wasn't to be.
"There's a sense of disbelief, no one was expecting this," CNN's Pedro Pinto said from the Danish capital. "Chicago was the favorite and to be knocked out in the first round, everyone had their jaws dropping down to the floor."
CNN's Ali Velshi in Chicago said there was an acceptance the city might not get the Olympics but absolute shock that it would fall at the first round.
People, Velshi said, were dumbfounded. "No one knew what was going on. They thought they must have misheard. There's some very hurt people around here." Watch the reaction in Chicago »
Tokyo -- which hosted the summer games in 1964 -- was next to be eliminated, leaving Madrid and Rio to battle it out in a thrilling last round of voting.
For many the bid from the Brazilian city represented the biggest risk, with security being one of the main concerns. Watch the reaction in Rio »
The enormous cost of staging the Games, in terms of improving a city's sporting and non-sporting infrastructure, puts a lot of pressure on the IOC to select the bid they feel is most capable of delivering success.
But the Brazilian pitch, made on the sentiment of the games being staged for the first time on a sports-loving continent, had clearly struck a chord with delegates, said Pinto.
"The margin of Rio's win in the final round -- 66 votes to 32 -- indicated that many IOC delegates had possibly made up their minds before cities began making their case in Copenhagen," he said.
"Jacques Rogge [the IOC president] before he took office, said that he would like to see Africa take the Summer Games and South America the Winter Games.
"It's a message of innovation and experimentation. They are opening up the Olympics to over 300 million people who live in this continent, 180 million of them who live in Brazil."
All four cities 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.
In the run up to the vote all four cities were viewed as strong contenders, experts said.
According to Ed Hula, editor of the Olympics Web site Around the Rings, the influence of Obama coming to Copenhagen was considered something that could put Chicago ahead. "It certainly gave them a lot of attention," he said.
However Pinto suggested some people in Copenhagen may have been upset Obama did not stay for the voting process. "He was here for just over four hours. The presence of Obama and his wife did not sway it at all."
Not to be outdone by Chicago's glitzy backers, Spain's King Juan Carlos and Queen Sofia and Spanish President Jose Luis Rodriguez Zapatero pushed the case for Madrid, while Brazilian President Luiz Inacio Lula da Silva and soccer legend Pele were joined forces to advertise the benefits of a Rio Games.
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.
Chicago's disappointment will be felt by Obama in particular -- he was born in Hawaii but spent much of his life in the city.
Many experts agreed it presented an excellent technical bid.
The Windy City has better hotels and a better venue lineup than Rio, Hula said. Almost half its proposed 31 venues already exist, and most would be located along the city's famous lakefront, close to the city center.
A Chicago Olympics would also have been advantageous to U.S. broadcasters, who provide big revenue streams for the Olympics, said Stephen Samuelson, the head of online sports at the Sydney Morning Herald in Australia.
"An American Games will produce a higher return for the IOC," said Samuelson.
For Rio, the major appeal is in bringing the Olympics to South America for the first time.
But Samuelson thought the IOC may have wanted to wait on giving Rio the Games until after Brazil hosts the 2014 football World Cup, so they can see how well the country deals with a major international sporting event.
But Hula pointed out that Rio's success in hosting the 2007 Pan American Games gave the city a level of experience that Chicago doesn't have.
Madrid's chances were seen to be hampered by a recent tradition that consecutive Olympics aren't staged on the same continent. The London 2012 Olympics will have happened just four years before 2016.
"If that bid had been on another continent it would have won," Pinto said, adding that for many at the announcement, Madrid was the strongest technical bid due to its public support, infrastructure and transport.
CNN's Melissa Gray contributed to this report.
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