WI never was, is not, and never will be a possibility.
Either the internals are telling him that he needs to get to WI to shore up some "soft" support or the margin is too close for comfort. In either scenario, WI is in play.
It may be revealing that, or it may be that Obama's campaign has a cautious strategy. Sure, it is almost getting to the point in the polling (that we see publicly), that he could spend a substantial portion of his last few days in North Carolina or maybe Florida, but to be honest I think that is a bad idea. Ohio/Wisconsin is where he should be even if he's five points ahead.
