If you are a Republican in the current environment, the first priority is securing Florida, then going after OH,IA, and VA. The GOP is mathematically out of the running without FL, and the Midwest is probably an easier region to flip than the Mountain West.
If you are Obama, your first priority should be securing PA, then VA and CO. If Obama wins those three, then he has been re-elected. With VA and PA, he needs just one of NM, NV, or IA to get to 270. Expect a lot of campaigning action in VA on both sides, and a lot of Republican activity in FL. Obama might be better off pulling some resources out of FL and using them to pin down CO, NV, NM, and NH. I expect FL to go Republican if the election is any closer than 2008.
Depending on how this union thing plays out, I think the absolute utter ceiling for any Republican is WI/MI/PA, with WI probably a bit easier than the other 2.
You can give up VA if you win WI. It's 3 less electoral votes, but those 3 aren't determinative. Either Iowa or Nevada would put you at 269 instead of 272, and 269 is still a GOP win.
