[UPDATE: the Bush campaign is in fact doubling its staff in New Hampshire while not reducing ad buys there. Guess we know where their firewall is now.]
The report is that the Bush campaign is yanking three million in ads from both Iowa and South Carolina markets to focus on ground game activities in Iowa. New Hampshire is - as of this moment - remaining untouched. The money will instead be used to put in more staffers in Iowa and Nevada.
Yanking the money from South Carolina is more relevant than doing so for Iowa itself, I think. I don't think that anybody was expecting Bush at this point to actually win Iowa, although he's going to need to do better than commonly expected there; but while South Carolina is generally considered to be prime social conservative territory it's not really what I would have called unfriendly territory for Jeb Bush, either. If he's yanking cash out of the market, it suggests that New Hampshire is going to be the Bush campaign's firewall. Whether or not that works is going to be one of the interesting questions of January.
PS: Since USA Today/The Des Moines Register brought it up: it is indeed interesting that Donald Trump is going to spend money now on ad buys in Iowa/New Hampshire/South Carolina. It's going to be expensive, though. You want to lock that ad time in early...