This story in today's Times nicely quantifies how Rudy's fortunes have changed--in New Hampshire, most immediately, but really across the country:

Mr. Huckabee’s rise also comes at a delicate time for Rudolph W. Giuliani, who has been slipping in national polls and who failed to lift his standing in New Hampshire with a heavy advertising campaign. Mr. Giuliani, a former mayor of New York, scaled back his campaign in New Hampshire to concentrate his efforts on the later states. ...

The Giuliani campaign believes that Mr. Huckabee’s momentum will fade. But its decision to scale back advertising in New Hampshire is telling. From Nov. 10 through Dec. 9, the Giuliani campaign spent $1.7 million on commercials in New Hampshire, compared with $1.3 million by Mr. Romney and $1.2 million by Mr. McCain, according to the Campaign Media Analysis Group, which estimates advertising expenditures.

Via Jonathan Martin, this Nashua Telegraph column (scroll down about a third of the way) says "scaling back" means cutting his Boston-based television advertising more than in half, but sticking with his previous ad schedule on New Hampshire's WMUR, the only statewide commercial station there.  

From what I can make out looking at this chart, Giuliani's heavy ad blitz coincided with a decline in his support from about 20 points to 17 or 18. The Giuliani campaign often argues that some states are naturally better-suited to him than others. But New Hampshire should have been a reasonably receptive state. The campaign may instead be brushing up against a different reality: That the more GOP voters in any state know about Rudy, the less they like him.  

Regardless of how Iowa turns out, I think we can now safely say there isn't going to be any Rudy momentum in New Hampshire, which, I think, makes it unlikely that Rudy gets momentum anywhere.

--Noam Scheiber