There was an analysis about why Rio was picked. I don't think the IOC is not Racist toward Obama. Just because he showed up in Copenhagen - it doesn't mean that all these voters have to be wow and vote against their principles.
. Chicago was eliminated not because of the city - but because of bad relations between the USOC and the IOC. There were bad blood, the war, economic crisis, geography of the city, ..etc & ... etc.
. Tokyo was just shadowed by the Beijing Olympic games last year.
. Madrid, although has many friends, but London is hosting in 2012. So they can't really have another games in Europe 4 yrs later.
So if you think about it, Rio wins by default, plus it's in South America - which is a region never host the games before - most Tokyo & Chicago supporters voted for Rio once those 2 cities were out of competition. Rio won because they have a flawless bid, citing that North America, Asia and Europe repeatedly hosted the games, it's time for Latin America to shine in the world stage in 2016.