Seven Republican presidential candidates took to the stage in Las Vegas on Tuesday night, the eighth debate so far, and wasted no time laying into hot-ticket issues including Herman Cain’s much criticized 9-9-9 tax plan, healthcare and Occupy Wall Street.

When asked by an audience member if she would prefer to discontinue the federal income tax and replace it with a federal sales tax, Rep. Michele Bachmann of Minnesota made an early jab at Cain’s plan, saying that the U.S. cannot give a 9 percent sales tax to Congress because then the rate would go up.

Former Sen. Rick Santorum of Pennsylvania added that the 9-9-9 plan means 84 percent of Americans would "pay more taxes,” referencing an independent analysis released Tuesday by The Tax Policy Center, which contradicted Cain’s claims that most Americans would see a tax cut.

Cain refuted the report and invited Americans to “do their own math” to see the truth. Former Massachusetts Gov. Mitt Romney compared Cain’s proposal to a "bushel basket" of taxes, saying that that people "don't want to pay both" state and federal taxes. Cain responded that other candidates were comparing "apples and oranges" when analyzing his plan and didn’t understand how it really works.

Perhaps the most explosive moment of the evening came when the conversation turned to healthcare. Santorum said Romney had no credibility because the plan he instituted in Massachusetts was the model for "Obamacare." The two sparred for several minutes, talking over each other before debate moderator Anderson Cooper could gain control. Romney, when given the chance to respond, said he never thought his Massachusetts plan should be instituted in the U.S., that it was the right plan for his state.

When the matter of Occupy Wall Street arrived, cheers erupted when Herman Cain said he stood by a statement made two weeks prior, where he effectively said Americans shouldn’t blame Wall Street for their financial woes, but blame themselves. Texas Rep. Ron Paul countered that many Americans are victims in the situation and that perhaps instead of looking to Wall Street for answers, protesters should turn to the Federal Reserve. Almost comically, Cain questioned protesters’ motives, asking, “What do the protesters want from bankers on Wall Street, to come downstairs and write them a check?”

Cain on Tuesday said the Occupy Wall Street activists should be camped out in front of the White House protesting President Barack Obama, not the bankers and investors in Manhattan. He says Obama and Washington politicians orchestrated the economic policies that the activists dislike.

(Photo: AP Photo/Chris Carlson)