Ever since the four cities bidding for the 2016 Olympics were announced in June of last year, Chicago has been the overwhelming favorite to be named the host city of the Games of the XXXI Olympiad. The race had tightened in recent months but the announcement that President Obama attended today's vote in Copenhagen (to mixed reviews) has once again shifted the odds heavily in Chicago's favor.

The Second City is a considerable favorite to win today, with a vast majority of bookmakers and Olympic observers fully anticipating a Chicago coronation this afternoon. Despite this, Fourth-Place Medal predicts that Chicago will lose in an upset today to Rio de Janeiro. It would be the first time in the 120-year history of the Olympics that South America would host a Games.

Chicago makes the most sense. As we've recounted in our previews for the past year, it will have been 20 years in between Olympics for the United States, the city has pre-existing infrastructure, its bid has a solid financial plan and, most importantly, the television rights to the Summer Games are up for renegotiation and having an American-based Olympics is sure to push the bidding between NBC and ESPN to unparalleled heights. Coupled with the popularity of Barack Obama abroad, Chicago seems to be a shoo-in. And if the IOC was voting on the safest bet, the American city would win in a landslide.

But the IOC doesn't always play it safe, particularly in recent years. Here are five reasons Rio could pull the upset:

1) Putting Rio on the world stage -- The IOC likes to fancy itself as a catalyst for world change and Rio provides an opportunity to provide such an impact. Members often tout the importance of awarding the 2008 Olympics to Beijing and boast about how this helped legimitize the "new" China to the rest of the world. The hope is that giving the Games to Rio will be revitalize the city, and Rio organizers have played on this "imbalance" claiming that the Olympics shouldn't only go to cities in rich, fully-developed nations. The message that "the Olympics belong to everyone, every continent, all of humanity," may be one that resonates with voters.

2) Anti-American sentiment within the IOC -- Obama's presence at the bid meeting today will make for a nice headline and photo op, but is it enough to reverse years of the American jealousy that permeates through the Eurocentric IOC? (Where 46 of 106 voting members are from European countries?) The Olympic governing body has long coveted the money the United States Olympic Committee gets from its TV deal with NBC. That battle only intensified this summer when the USOC blatantly defied the IOC and went ahead with plans to launch its own television network. They eventually reached a detente, but the resentment lingers. Two years ago baseball and softball were pulled from the Olympic program. It's no coincidence that both sports are associated with the United States. A vote for Rio (or Tokyo or Madrid) might be more of a vote against America than anything.

3) Chicago apathy provide stark contrast to Rio enthusiasm -- As we detailed earlier in the week, citizens of Chicago are sharply divided about the city's bid proposal. There are many passionate supporters, to be sure, but the perception in Copenhagen is that the city is ambivalent about the games. On the other hand, a public holiday was declared in Rio today so citizens could participate in a party that is expected to draw 100,000 to Copacabana beach. Rio is playing up the party atmosphere and flair of its bid. Chicago has Oprah. Which will voters respond to more? Enthusiasm of hundreds of thousands of residents or the enthusiasm of a few, very famous ones?

4) The IOC doesn't like to be told what to do -- Call it stubbornness or resistance to conform, but the IOC has made a habit of bucking popular wisdom. It was all but assured that Athens would get the centennial Games in 1996, but Atlanta won out. Paris was the heavy favorite in 2012 before getting upset by London. And Sochi, Russia figured to be third out of three in the running for the 2014 Winter Olympics yet squeaked by PyeongChang, South Korea to get the bid. The IOC is unpredictable and Rio is the unpredictable choice. Media, especially American media, has all but given the Olympics to Chicago particularly after the president gave his talk today. Might some IOC members resent having their decisions made for them? Or is Obama that transcendent in Europe?

5) It works for American TV -- One of the biggest pluses for Chicago's bid is the fact that American TV rights for 2016 will go up for bid after the Vancouver Olympics. There is expected to be a fierce bidding war between NBC, ESPN and, perhaps, Fox. And while it's true that Chicago is the best-case scenario for American networks, Rio also works since the city's time zone is just one hour ahead of New York. This would allow for the live primetime broadcasts that American networks crave.  

There are just as many reasons why Rio won't get the bid. These include the bid's huge budget, concerns over crime and the little pre-existing athletic infrastructure in the country. That's why Chicago is the oddsmaker's favorite and is expected to get the nod. 

But funny things happen in these IOC meetings, particularly with the round-by-round eliminations that take place. Allegiances tend to shift once the choices narrow. It's not as much about who more people like at the beginning of voting, it's about which city supporters of the eliminated candidates flock to. Three times in the past five Summer Olympics bids, a city that has won early rounds of voting was upset in the final (Athens, 1996; Beijing, 2000; Madrid, 2012).

While nobody seems to think Tokyo or Madrid has much of a shot, there's still the possibility that one of those cities could shoot to the top if one of the favorite (Rio, in particular) is more everybody's second-favorite choice rather than their first favorite.

But, still, this is Chicago's race to lose. The decision the voting IOC members will have to make is whether to go with Chicago's momentum, practicality and stars or whether the opportunity for change in Rio de Janeiro potentially caused by the Games is enough to outweigh any possible problems. 

We think it will be the latter. While both would be fine choices, and it's hard to pick against Chicago's political machine, we think that the potential to impact chage will be too hard for the IOC to pass up and that we'll see Rio de Janeiro in 2016.