Jim Cole / AP Photo

HANOVER, N.H. — Having catapulted into the top-tier of the Republican presidential field, businessman Herman Cain took an opportunity at the seventh debate of the primary season to tout his signature “9-9-9? economic plan . That is, when he wasn’t defending it from withering attacks.

“What 999 does — it expands the base,” Cain said on a debate stage in New Hampshire tonight. “When you expand the base, we can arrive at the lowest possible rate, which is 9-9-9.”

Several of his rivals seemed unsure about their approach to the ascendant former Godfather’s Pizza CEO , who is running in second place in recent national polls. Jon Huntsman referred to Cain’s plan, which would lower the current 35 percent corporate tax rate to 9 percent, swap the personal income tax system for a 9 percent flat tax and create a 9 percent national sales tax, as “a catchy phrase.”

“In fact, I thought it was the price of a pizza when I first heard about it,” Huntsman said.

Cain shot back, “It is not the price of a pizza, because it has been well-studied and well-developed.”

In a half-joking, half-serious moment, Minnesota Rep. Michele Bachmann said, “When you take the 9-9-9 plan and you turn it upside down, I think the devil’s in the details.”

Former Pennsylvania Sen. Rick Santorum called Cain’s plan “naïve.”

Even frontrunner Mitt Romney told Cain that “simple answers are — are always very helpful, but oftentimes inadequate.”

The debate, sponsored by the Washington Post and Bloomberg and held at Dartmouth College, featured eight of the Republican presidential contenders and focused on economic issues.

It was the most intimate debate setting yet, with the candidates seated around a wooden table just inches away from each other and the moderators. In one portion of the exchange, candidates were allowed to question each other.

It was an important night for Cain, who has not received the same level of scrutiny as other leading candidates so far. It was also viewed as a pivotal moment for Texas Gov. Rick Perry, who had stumbled over his answers in previous debates.

But Perry seemed to recede into the background.

In an attempt to dip his toe into a two-hour session largely dominated by Cain and Romney, at one point Perry offered a “gotcha” question to the former Massachusetts governor.

“Governor Romney, your chief economic adviser, Glenn Hubbard, who you know well, he said that Romneycare was Obamacare,” Perry said. ” And Romneycare has driven the cost of small-business insurance premiums up by 14 percent over the national average in Massachusetts. So my question for you would be:  How would you respond to his criticism of your signature legislative achievement?”

Romney brushed off the comment, telling Perry, “You know, the — the great thing about running for president is to get the chance also to talk about your experience as a governor.  And I’m proud of the fact that we took on a major problem in my state.”

But when Perry interrupted the answer, Romney fired back: “I’m still speaking. We — we have — we have less than 1 percent of our kids that are uninsured.  You have a million kids uninsured in Texas.  A million kids.  Under President Bush, the percentage uninsured went down.  Under your leadership, it’s gone up.”

“I care about people.” Romney continued. “Now, our plan isn’t perfect.  Glenn Hubbard is a fine fellow.  Take a look at his quote.  Some people say that.  Just because some people say something doesn’t mean it’s true.”

At another point Romney was asked if he would support another Wall Street bailout. His response: “Nobody likes the idea of a Wall Street bailout, I certainly don’t.”

But then he went on to say that in 2008, at the height of the economic crisis, “action had to be taken.”

“Was it perfect? No. Was it well implemented? No, not particularly,” he said.  “Should they have used the funds to bail out General Motors and Chrysler?  No, that was the wrong source for that funding.  But this approach of saying, look, we’re going to have to preserve our currency and maintain America — and our financial system is essential. “