Wisconsin, Michigan, Minnesota, Oregon, Pennsylvania, and Washington if McCain is the nominee.
If a state won by Kerry by 7 points while Bush won by 2 is in play, who cares what state is Ohio? Obviously, the assumption here is that the election is close and a state like Ohio would actually matter. If Washington is in play, it's probably not a very close election.
What Republican candidates can carry Washington?
I think the "Ohio" will be Wisconsin. WI has been THE state with the tightest margin of victory for two elections now. Just the slightest breeze could push that one into the Republican column