Responding to my last item, commenter joebeek makes an excellent--and embarassingly (for me) obvious--point about why it makes a lot more sense for McCain to focus on PA over NH and ME-2:
I guess they're thinking that while New Hampshire by itself is [an easily-turned] "sailboat", the combination of New Hampshire, Virginia and Maine's northern district (18 EV) is no easier than winning Pennsylvania (21 EV). Basically, if they pull off the unlikely feat of winning PA, they dont need either VA or NM, IA and CO anymore.
The go-north strategy assumes McCain thinks he can hold Virginia. But, even though VA wasn't named in yesterday's CNN story about states at least one McCain insider considers "gone," his chances there are looking awfully bleak, even if you assume a surprise Bradley effect. If Virginia's gone, too, then PA really is McCain's last shot.