In their most spirited debate yet, Tuesday night the Republican presidential aspirants immediately drew first blood from Herman Cain over his 9-9-9 tax plan, which has been a key component of Cain’s rise in the polls and has forced his rivals to take him more seriously.

Almost everybody on stage had something bad to say about the plan, which would replace income and payroll taxes with a flat 9 percent tax on corporate and individual incomes and institute a national sales tax. Many pointed to a report by the Tax Policy Center that says the plan would raise taxes on 84 percent of U.S. households.

Minnesota Rep. Michele Bachmann repeated a prior claim that it’s a tax plan, rather than a jobs plan, and said that under certain circumstances Washington lawmakers might even increase rates, which would hurt businesses.

Texas Rep. Ron Paul said that the plan is dangerous and regressive.

When Cain argued that his opponents simply don’t understand the plan and were misinterpreting it, mixing apples and oranges, Mitt Romney countered that Americans would be taxed on apples and oranges because in most states they would have to pay the additional tax. Cain pretty much shut down after that.

Romney had several clashes with Texas Gov. Rick Perry, who was under pressure to perform better and frame his arguments more coherently, which he did, but only marginally so. The most heated exchange was when Perry tried to slam Romney’s record on immigration by bringing up an old Boston Globe report indicating that Romney had hired illegal immigrants and calling him “the heighth [sic] of hypocrisy.”

“Mitt, you lose all of your standing from my perspective because you hired illegals in your home, and you knew for about it for a year,” Perry said.

Romney has said all along that the lawn service he employed hired undocumented workers, and when he found out, he fired them. When Perry continued to hammer his point, repeatedly interrupting, Romney became rather condescending, noting that the Texas lawmaker had previously had “a tough couple of debates,” so it was understandable that he would be “testy.”

“You have a problem with allowing someone to finish speaking,” Romney said. “And I suggest that if you want to become president of the United States, you got to let both people speak.”

The former Massachusetts governor also took the usual hits on the mandatory health care law that he enacted while in office. “You just don’t have credibility, Mitt, when it comes to repealing ‘Obamacare,’” Rick Santorum said. But Romney hit back just as hard, and perhaps most importantly, he was not the usual dullard that voters have perceived him to be and proved that he can be as feisty as his opponents.

Jon Huntsman opted not to participate in the debate in protest of Nevada’s decision to move the date of its caucus, which has complicated the GOP’s voting schedule. The other bottom-tier candidates, Santorum, Bachmann, Paul and Newt Gingrich, each delivered a strong performance, but probably not strong enough to push them to the top.

(Photo: Ethan Miller/Getty Images)