We turn again to Jonathan Martin for a good summary of what was behind Rudy's intense campaign swing through New Hampshire this weekend--and his even more intense attacks on Mitt Romney there:
The decision to go on the attack, a clearly calculated move, is striking for at least two reasons.
First, Giuliani's rhetoric — along with his three-day, retail-heavy visit and expansive ad buy here — signals that he recognizes the importance of winning or at least finishing strong in one of the two traditional kickoff states.
Romney, as Giuliani pointedly noted later in the chat, is not (at least right now) a threat in the later, larger states where the former mayor has spent considerable time and where he enjoys commanding double-digit leads.
Further, by narrowing his critique to just Romney and essentially waving off the opportunity to contrast his record with other GOP rivals, Giuliani makes plain that he believes Romney is a threat and likely the most significant one to his winning the Republican nomination.
Check out this RCP polling graph to see why Rudy's getting nervous about New Hampshire.
(Photo from a Laconia, NH, VFW post)