I recently read 'Inside the Olympics' by former IOC member Dick Pound. Pound wrote that there is a large portion of the vote for host cities based on technical merit: arenas, hotels, airport, transportation, security, financial stability, etc. Then the IOC members (are supposed to) vote based on their visits to candidate cities. They are to evaluate each city's ability to host the Olympics and Paralympics. Somehow these components are combined and, from behind the secret curtain, the new host city emerges.
Pound implies that the recent addition of technical merit was done to provide some objectivity, a refreshing change from the way they used to be. The IOC definitely was, and to some extent remains, an old boys club. That meshes with what David Maraniss, author of 'Rome 1960' said at a book talk I attended. He said that when Avery Brundage was IOC president and you wanted to host the Olympics, you needed "the three B's: booze, broads, and bucks." Brundage enjoyed expensive alcohol, expected handouts, and was an unrepentant womanizer. Somehow he managed to carry on multiple affairs while married and fathering two children with his Scandinavian mistress.
I suspect that going forward, financial stability will play a larger role. Madrid is in the running for the 2020 Olympics, but because of their financial woes, they may be forced to do a lot of unpopular things to remain in the Euro. Spending billions during that time won't go over well. Usually such practical reasoning carries no weight with the IOC, but this is about money. They just might sit up straight and listen to this.
I'm an Olympics junkie.