Why should this election be as close as it appears to be from early polls? Rendell has not done spectacularly badly as Governor, has he?
He hasn't done anything terribly bad or very good. All in all, he's been a mediocre governor and has mainly failed to deliver on the big PA issue, property tax reform.
Right now, Swann's upsides are showing, mainly his charisma, name recognition, and newness to the political scene. Once the campaign gets going, I'd expect his negatives to become apparent, especially his lack of policy background.