Obama may win the election. But it's very close right now.
One of the calculations of the McCain campaign has been to concentrate all their resources on the closest states, and they have been successful in staying close, tied, or ahead in the states he needs to win. So while McCain trails slightly nationally, he leads in NH and he's on the cusp of victory in Pennsylvania.
Obama has tried to widen the playing field and worked hard to get NC and Indiana in play.
Look, if Obama wins the popular vote by 5% NC and Indiana won't matter. But if the popular vote is very close, NC and Indiana will go to McCain despite all Obama's efforts.
If he doesn't have a very solid lead, then he's behind in PA, as long as voter fraud is so rampant.
The Philly suburbs are largely Obama-supporting, too.