Jay Cost does an excellent analysis of Obama’s and McCain’s strengths/weaknesses and the look of the map of Ohio for the 2008 Election. See here.
The most recent poll has Obama up 8 in Ohio, but I can’t imagine that number holding (minus an absolute landslide victory) in November. I think the advantage is still Obama’s, but not that wide of a margin and McCain is not without the possibility of an upset here.
One of the keys to watch will be (as Cost correctly notes) if Obama can minimize his damage or even possibly pull even (in which case he wins for sure) in the suburbs of Cincinnati and Columbus. Obama will have trouble in Southeastern Ohio (where Hillary was super-strong). McCain could likely poach there.
The X Factor for Obama is going to face is that in his base areas around Cleveland thousands are now living in homeless shelters as a result of one of the biggest outbreaks of foreclosures in the country. Entire neighborhoods in the Cleveland suburbs are now vacant. Getting voters in the midst of massive life crisis/transition will be very difficult and could seriously undermine his efforts. If it’s close already this could spell trouble for him.