First of all, Chicago is about 90% Democrat. We have a single Republican alderman (out of about 50, if I recall correctly) and he represents the area by O'Hare, which is pretty much outside the actual city. But only about 50% of the population supported the bid for the Olympics.
I was ambivalent towards the whole thing. On the one hand, as an architect, the Olympics could have been great for business. However, it was ahuge gamble on Chicago's part. There's no guarantee it would have been profitable. And there was no guarantee it would have helped the famously poor and violent South Side (more deaths in 2008 than in Iraq), which is where a lot of the Olympic venues would have been located. There were theories that it would have led to the relocation of massive amounts of people who rely upon public housing to the suburbs in order to create a better perception for the TV. Lots of Democrats (and Republicans and Independents, etc etc) were opposed to the Olympics because of those reasons.