Las Vegas (CNN) - Former Godfather's Pizza executive Herman Cain was at the center of a pile-on Tuesday night at the presidential debate hosted by CNN and the Western Republican Leadership Conference, as his GOP rivals took turns picking apart his "9-9-9" plan to reform the United States tax code.
Cain's plan would throw out the current tax system and install a 9% corporate income tax rate, a 9% income tax rate and a 9% national sales tax
The other six Republicans on stage at the Venetian resort in Las Vegas, who have watched Cain soar to the top of the polls in recent weeks thanks to his straightforward message and outsider image, were united in calling the tax plan simplistic and risky.
"There are much more complexities than Herman let's on," said former House Speaker Newt Gingrich.
Texas Rep. Ron Paul called the plan "dangerous" and said it would increase taxes on low-income citizens.
Texas Gov. Rick Perry turned to Cain directly and told him that voters "are not interested in 9-9-9, what they are interested in is flatter and fairer."
"I will bump plans with you brother, and we will see who has the best idea about getting this country working again," Perry said. "It's not going to fly."
Former Massachusetts Gov. Mitt Romney said Cain's plan would add federal taxes on top of state taxes.
Cain said his plan would not raise taxes on poor people, and said his opponents were misrepresenting his plan.
"The reason my plan is being attacked so much is the lobbyists, accountants and politicians, they don't want to throw out (the) current tax code and replace (it) with something that's simple and fair," Cain responded.
They were joined on the stage by former Pennsylvania Sen. Rick Santorum and Minnesota Rep. Michele Bachmann, who also attacked the Cain plan.
Former Utah Gov. Jon Huntsman chose to boycott the debate because of a dispute between Nevada and New Hampshire over the GOP primary calendar. Huntsman is staking his campaign on a win in New Hampshire and held a town hall there Tuesday night instead.
–CNN's Kevin Bohn contributed to this report.