Europe wakes up with a hangover.
My biggest worry, in fact, is that Mr Obama wins and the Democrats get a huge majority in Congress. The new president will be focused hard on two big policy challenges in Washington - dealing with Iraq and reforming US healthcare. He won't have a lot of political capital to spare to stand up to a resurgent Democratic Party in Congress over trade policy, and the US could slide further towards protectionism.
Meanwhile, a big Republican defeat in November is quite likely to result in a very nasty isolationist turn inside the opposition party. The neoconservatives - those bad guys who believe that the US should spend blood and treasure trying to bring democracy to the great unwashed - will be discredited. President Obama could find himself under pressure from both parties in Congress to put US interests first.
All of this means that the new president will have to spend a fair amount of time on trips to Europe explaining to his admirers why he really isn't able to deliver that much.