As Rio de Janeiro revels and rejoices in a runaway victory for the right to stage the 2016 Olympics, a chill wind is blowing through Chicago, seen by many as favourites before Friday's stunning IOC vote.

So did Rio win it or did Chicago blow it?

The question has been much debated in the corridors and meeting places around the Olympic Congress in the 48 hours since the International Olympic Committee (IOC) chose Rio by 66 votes to Madrid's 32 in the final voting round after eliminating Chicago, astonishingly, in the first round, and Tokyo.

The easy answer would be to say it was a bit of both.

While IOC members and observers can find reasons why Chicago flopped, despite the spectacular intervention of U.S. President Barack Obama, there is virtual unanimity in the view that it was Rio who won it, and won it in style and on merit.

Rio had the best presentation and the best arguments and deserved to win, former IOC vice-president Kevan Gosper told Reuters.

The Brazilian team's 45-minute presentation to the IOC was powerful and passionate and described by seasoned observers as the best they had ever seen.

Evocative videos showed Rio at its colourful and irresistible best, a place of glorious scenery, beaches, mountains, fun, frolics and a joyous and exuberant population.

NEW GROUND

Their X Factor was the passionate advocacy of Brazil's charismatic president Luiz Inacio Lula da Silva, who argued the case for the IOC to break new ground and take the Games to South America for the first time, moving away from the endless round of Olympics in North America, Europe and the Far East.

He pointedly referred to the fact that the U.S. had already staged eight Olympics and even borrowed Obama's Yes we can election slogan.

Lula said: The opportunity now is to extend the Games to a new continent. It's an opportunity for an Olympics in a tropical country for the first time, to feel the warmth of our people, the exuberance of our culture and the sensation of our joy.

He also leaned heavily on the argument that Brazil was the only one of the world's top 10 economic powers not to have staged the Olympics.

IOC executive board member Richard Carrion said the fuss about Obama's visit had played no role. I think we are giving too much importance to the head of state visits. I think it was more the strength of the Rio bid, he added.

We wanted Obama to come. We needed him to come so there were no excuses, said Rio bid leader Carlos Nuzman.

TRUE SHOCK

Rio may indeed have won on merit but Chicago's abject showing was a true shock, with the city picking up a mere 18 votes despite the presence for the first time of a sitting U.S. president and an eloquent speech from the first lady.

An official with the Chicago bid told Reuters that the worst thing about losing was having to put up with a succession of IOC members lecturing you on where you had gone wrong.

It was a pretty long list though no one seemed to be blaming the Obamas, at least.

Among issues mentioned were a lacklustre presentation which seemed to rely entirely on the Obamas, a long-running dispute between the IOC and the United States Olympic Committee (USOC), continual changes of leadership at the USOC, and complacency about the strength of the bid.

Gosper said tactical voting was almost certainly to blame for Chicago's early elimination. He said Rio and Madrid had secured first-round votes because they had long-established figures within the IOC speaking for them: former FIFA president Joao Havelange for Rio and former IOC president Juan Antonio Samaranch for Madrid.

I believe there was some tactical voting to support Tokyo in the first round as reward for a good bid which could not win in the end because it was too soon for Asia after Beijing, he said.

But the members should have thought it through. It produced a highly unfortunate outcome.

It was an insult to the biggest national Olympic committee and the one which brings in the most revenue to let Chicago go out early.

It was not the way to treat the president of the United States who had come in person to reach out to us.

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