Over on the Stump, Noam agrees with one of our favorite commenters, Aeromonas, in his contention that it is a mistake for McCain to focus on Virginia, because "it's hard to imagine a scenario in which Obama wins Virginia but loses Ohio."
In response, commenter AlanSP takes a page from football strategy to explain why Obama could change the landscape:
Aeromonas's reasoning is probably more true of states within the same region than states from separate regions. For example, to oversimplify a bit, Indiana is pretty much like its midwestern neighbors, but more conservative. It's highly unlikely that Obama would win Indiana but lose Ohio or Michigan. I'm not sure if the same reasoning holds when comparing states from different regions. The things that matter in the Midwest (e.g. manufacturing jobs) are different from the things that matter in, say, Alaska (e.g. the environment), which are probably different from the things that matter in Virginia (I actually don't really know what the big issues in Virginia are. Maybe Rhubarbs or virginiacentrist can fill us in). So depending on Obama's message, it's possible to see him overperforming in some of those regions while underperforming in others.
The other thing to keep in mind is that campaigns matter, particularly when one person is campaigning and the other isn't. The fact that Obama blew off Kentucky and West Virginia was a big reason why he got beaten so badly in those states, just like the fact that Hillary blew off a lot of the caucus states was a big reason why she got crushed in those states. All else being equal, Virginia is probably a bit more conservative than Ohio, but having a contested campaign in one state and an uncontested campaign in the other is a pretty clear violation of the "all else being equal" assumption.
A sports analogy would be the spread offense in football. When a team plays 4 or 5 receivers, usually there are one or two that are clearly better than the others (using the 2007 Patriots as an example Randy Moss and Wes Welker were much better than Donte Stallworth and Jabar Gaffney). However, if you leave the weaker receivers completely uncovered, they will shred your defense. Same deal with leaving states uncontested (in this analogy Moss = Ohio, Welker = Michigan, Stallworth = North Carolina, and Gaffney = Georgia). The problem for the defense is that the need to devote defenders to weaker threats means that you can't focus as much of your coverage on Randy Moss as you'd like. It's difficult to defend.