@JPB,
It often comes down to this.
Huntsman can't remain on the fringes and the GOP won't even let him if he's too far out on the fringe (i.e. debate invitations) and so he has to go for broke in a state in which he thinks he has some chance.
The obvious downside is that while he is working the hell out of New Hampshire, everyone in the rest of the country is forgeting about him. If he pulls off a miracle in NH what are Republican voters going to say:
"So this is where the guy went for all this time. Pretty crafty. I'm going to have vote for him my state's primary!"
or
"Geez what does the Granite State know that us South Carolinians or Floridians don't know. I'm going to have to really start listening to this guy and completely change my mind in the next 30 days."
The chances of him beating Romney in NH are so slim and the national benefit he accrues if he does is so meager that not only do you know that this is his Hail Mary pass, but that he's decided he's not dipping into the family fortune to keep the ride going.
At least spending the rest of the year in NH should be pretty pleasent. I hear there's even some people up there that speak Chinese.