Depending on how the rest of the year pans out, Obama could coast to a five or six point win or Romney could take it by between 3 and 4. I assume both sides will campaign well, so circumstances will do a lot of the deciding, with some basic brain psychology thrown in, as always.
I just don't feel good about the legislative aftermath in either scenario. Either Obama wins and faces a split Congress or perhaps even a Republican House and Senate, or Romney wins and he gets a TEA-Party influenced House and a narrow GOP Senate where the Dems hold a filibuster. Either way, we get a whole lot of nothing done for a while again. When people say that the election will decide which policy course the country will take, I don't see that happening in any clearcut way.
Which is why I find all of the Romney-worship going on here so ridiculous... and why I found a lot of the Obama-worship back in '08 equally so. The President can do nothing by sheer will, he requires Congress and Congress has rarely been this bloody-minded.