Yet the 24 hours before the New Hampshire primary were a case in point as to how even a largely sewn-up contest could become a headache for the former Massachusetts governor. In the space of a single day, Romney found himself under attack from one opponent (Gingrich) for his work in private equity, mocked by two others (Huntsman and Rick Perry) for a gaffe about firing health insurance providers and learned that a super PAC supporting Gingrich was going up in South Carolina with $3.4 million in negative ads…

Of the candidates still hoping to overtake Romney, Gingrich is the one who inspires the most concern among Romney loyalists. A former House speaker and prominent television commentator, Gingrich has the universal name recognition and brawler’s personality it would take to compete with Romney over the long haul.

And even if his campaign ends up running on fumes, Gingrich has been in such straits before — he was counted out of the competition last summer when nearly his entire staff resigned, and doggedly hung in the race long enough to make a comeback. His exhortation to Romney in Sunday’s NBC debate to drop his “pious baloney” struck some Republican presidential operatives as a sign of things to come.

“There’s a [concern] that unlike everyone else, Newt really does think he has nothing else to lose,” said one Romney supporter. “Newt could become his own IE [independent expenditure committee].”