It's going to be decided by a few hundred thousand voters in a select few states. The popular vote will be close ... my prediction is Obama 49%, Romney 47%. The electoral college will be closer, but Obama will win with about 300.
There are about 11 toss up states. If they all end up leaning the same way as 2008, Obama will win in a landslide. If they all end up leaning the same way as 2004, Romney will pull off the upset.