Have you suffered some sort of brain damaging accident that I should know about? I just got done telling you that McCain's primary task is to hold every red state and Obama's primary task is to take a red state away. If their positions were reversed, they would probably still be in the same states as Obama tried to pull an upset in a red state.
It's like an NFL team that has a slight lead going into the last few minutes of the fourth quarter. If they have the ball, they're not going to start throwing a lot of long balls. Oh, they'll go for a touchdown or field goal if they can take it, but if they have a choice between a fierce but risky attack and protecting the ball and running the clock out, they'll be on defense while on offense.
As the Republican, McCain has a batch of red states that already add up to more than 270, and he has an energized base. Even if his internals showed him up by 5 or so, he'd be an idiot to try to take away some blue states. Pennsylvania is the possibility of a rushing touchdown to put the game away.
Got it now?