I always thought Obama's performance in Ohio in general was very poor when you consider just how bad the state economy was. The fact that 47% still wanted the Republicans in charge after Bush + Iraq + the state economy + the meltdown + the loss of manufacturing jobs throughout the decade does not speak well of Democratic strengths in the state.
Its true he didn't do as well as some might think, although I think this was a state more suited to a Hilary Clinton type Democrat as opposed to Obama one. Also McCain campaigned quite heavily in the state in the final month while Obama did some but not quite to the extent of McCain. Relative to Pennsylvania, his numbers were reasonable as the Republicans always perform slightly better in Ohio than Pennsylvania, although the difference in Republican performance between Ohio and Indiana was rather small as normally the Republicans do quite a bit better in Indiana. Although Obama did campaign there a fair bit while I think most Republicans just assumed they would win the state as they always have.
Also, Obama is black, you see. It wasn't a major factor, but it was a factor.