The caveats: I'm not a scientist, these numbers are approximations based on early voting data and the final numbers from 2008. These numbers do not figure in any 3rd party candidates.
Early voting in Ohio are showing "Red" counties generally up by 120%, and early voting in "Blue" counties roughly 80% of what it was in 2008.
Obama won "Blue" counties by and average of 55.87% in 2008. McCain won "Red" counties by approximately 58.1% in 2008. If you apply turnout projections and keep the same level of support you get:
The difference is 109,559 votes.