Last night’s Republican presidential primary debate in New Hampshire — it was hosted by Bloomberg/Washington Post and focused on economics — should have been a dangerous one for Mitt Romney: He is the runaway frontrunner, especially after New Jersey Governor Chris Christie endorsed him earlier in the day — and the “Occupy Wall Street” protests have opened up new space for attacks that the one-time private equity executive is out of touch.

But the former Massachusetts governor may just be as untouchable as his perfect head of hair. As he looked on, the rest of the Republican field seemed content to pile on former pizza executive and longshot candidate Herman Cain’s wacky “9-9-9” tax plan. “They see Herman Cain rising and rising and rising, and he’s the one collecting all the votes,” Republican pollster Frank Luntz told The National Memo.

Romney was grilled about his support for the 2008 bailout of Wall Street (a major cause of suspicion from the tea party base), and whether a European economic collapse would prod him to take the same kinds of action that the Bush Administration took in late 2008. “Action had to be taken,” he said, before delivering some mild criticism of how the money was spent and describing his Ivy League advisers.

By framing his support for the bailout in terms of protecting “American currency,” Romney may have deflected some attacks from the likes of Texas Governor Rick Perry. “It was the best answer he’s given on that topic so far,” said Luntz. “Wall Street is increasingly unpopular.”

The rise of Cain, however, clearly has the also-rans in the Republican field more concerned than the financier campaigning in their midst. Perry attacked Cain’s tax plan — as did Rick Santorum — and Michele Bachmann even made a reference to Satan’s favorite number. “When you take the 9-9-9 plan and turn it upside down,” she said. “I think the devil’s in the details.”

As Luntz — who has run on-air focus groups for Fox News that often result in what seems like a disproportionate number of Cain supporters — pointed out, Cain’s recent surges in the polls and his emergence as an actual force who could surprise in Iowa have made him a much more existential threat to the campaigns that are trying to rely on the momentum of the Tea Party. “It’s easy to get votes from a candidate when they just switch to a candidate,” Luntz said. By going after the former CEO of Godfather’s Pizza, the GOP last night proved that everyone, except for Romney, is shooting for second place and hoping for the best.