"My advisers come from the American people," Cain said Tuesday night at New Hampshire's Dartmouth College in the seventh debate of the Republican nominating contest. The debate focused on the economy.
"I also have a number of other economists who helped me with this 9-9-9 plan," he said. "It didn't come off a pizza box."
The plan -- which calls for reducing the individual and corporate income taxes to 9 percent and introducing a 9 percent national sales tax -- was criticized and derided by the other GOP presidential hopefuls in the 2-hour roundtable debate sponsored by Bloomberg News and The Washington Post.
"I think it's a catchy phrase -- in fact, I thought it was the price of a pizza when I first heard it," former Utah Gov. Jon Huntsman Jr. quipped minutes after former Sen. Rick Santorum of Pennsylvania suggested the plan would either die in Congress or hand Democrats another way of taxing Americans.
Cain said in response, "9-9-9 will pass, and it is not the price of a pizza, because it has been well studied and well developed."
Rep. Michele Bachmann of Minnesota said, "When you take the 9-9-9 plan and you turn it around, the devil is in the details."
Texas Gov. Rick Perry said: "I don't need 9-9-9. We don't need any plan to pass Congress. We need to get a president of the United States that is committed to passing the types of regulations, pulling the regulations back, freeing this country to go develop the energy industry that we have in this country."
Santorum later said to Perry, "I don't want to brag, Governor, but Pennsylvania is the gas capital of the world right now, not Texas."
Huntsman tried to make a joke from that -- and got a bit of a laugh -- saying, "Washington, D.C., is the gas capital of the country." The camera panned to Perry, who rolled his eyes.
The candidates joined in a chorus of criticism of the Federal Reserve System and Fed Chairman Ben Bernanke.
Rep. Ron Paul of Texas accused the Fed of covering up its actions as the economic crisis worsened. Cain, who served on the board of the Federal Reserve Bank of Kansas City in the 1990s, said, "I don't agree with the actions of this Federal Reserve."
Former House Speaker Newt Gingrich said Bernanke should be fired.
"If they want to really change things, the first person to fire is Bernanke, who is a disastrous chairman of the Federal Reserve. The second person to fire is [U.S. Treasury Secretary Timothy] Geithner," Gingrich said.
"If you want to put people in jail, I want to second what Michele [Bachmann] said," Gingrich added. "You ought to start with [Rep.] Barney Frank [D-Mass.] and [former Sen.] Chris Dodd [D-Conn.]," Gingrich said.
Those lawmakers wrote the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010, touted as the most sweeping change to U.S. financial regulation since the Great Depression, affecting all federal financial regulatory agencies and almost every aspect of the U.S. financial-services industry.
Frank told the liberal Talking Points Memo Web site Republicans controlled the House from 1995 to 2007 and the Senate for most of that time. He ridiculed Gingrich's complaint.
"It's interesting, the charge is failure to stop Newt Gingrich and Tom Delay (R-Texas, former House Majority Leader) from deregulating," he said. "This notion we caused the problem that started while they were in charge even by Gingrich's standards is very odd."
Romney defended elements of the 2008 Wall Street bailout as an imperfect but necessary solution.
"My experience tells me that we were on the precipice and we could have had a complete meltdown of our entire financial system, wiping out all the savings of the American people," Romney said. "So action had to be taken."