President Obama had campaigned for Chicago, but to no avail. Of course, now people are wondering about the political implications. Conservatives were thrilled that Obama suffered a defeat on the international stage.
But Obama was damned if he did, and damned if he didn't. If he hadn't gone to Copenhagen and Chicago had lost, conservatives would have been critical of him for not making the effort, and they would have blamed him for the loss. They would have said that he doesn't really care about America, that he only wants glory for himself, that the Olympics wouldn't matter to him because he'll be, at best, a lame duck in 2016, etc. If he hadn't gone, and Chicago had won, conservatives would have said that America didn't need his sales pitch, that we can do fine without him. If he had gone and Chicago had won, they would have said he was wasting his time, that Chicago would have won whether or not he was there. Conservatives would have done everything possible to either blame him for the loss, or deny him praise for the victory.
I think most fair-minded people will say that at least Obama gave it a shot. "Fair-minded people" being people who don't automatically hate Barack Obama. Which, in my opinion, is actually the vast majority of the American people.