Washington (CNN) -- It got personal for the Republican presidential field Tuesday night.
After previous debates that seemed tame by comparison, the Las Vegas showdown among seven top contenders turned downright nasty.
Texas Gov. Rick Perry accused former Massachusetts Gov. Mitt Romney of lying about hiring illegal immigrants. Romney cited Perry's shaky prior debate performances and how Perry once was a Democrat backing Al Gore.
Former Pennsylvania Sen. Rick Santorum attacked Romney's sincerity in opposing President Barack Obama's health care reforms, and described the three GOP frontrunners -- Romney, Perry and former Godfather's Pizza CEO Herman Cain -- of being pro-business candidates who supported bank bailouts.
Throughout the 90-minute debate held by CNN and the Western Republican Leadership Conference, candidates cut each other off or talked over each other in chaotic exchanges.
It all led former House Speaker Newt Gingrich to caution his rivals in the end to refocus their rhetoric or risk trivializing the campaign.
"Let me just point out for a second that maximizing bickering is probably not the road to the White House," Gingrich said to applause.
CNN political contributor David Gergen agreed, saying after the debate: "These fisticuffs are bad news for this party."
The crowd at the Las Vegas debate didn't seem to mind, often cheering for competitors or booing either questions asked or answers provided.
Romney, a consistent front-runner considered the candidate to beat, came under repeated attack and mounted his most spirited defense of the campaign so far.
When Perry repeatedly cut off his attempts to answer accusations of hiring illegal immigrants, Romney fired back.
"You have a problem with allowing someone to finish speaking, and I suggest that if you want to become president of the United States, you have got to let both people speak," Romney said.
Earlier, he alluded to Perry's recent plunge in the polls after weak debate performances.
"This has been a tough couple of debates for Rick, and I understand that," Romney said. "And so you're going to get testy."
Perry went for Romney's jugular on immigration, saying he lacked any credibility on the issue because he hired illegal immigrants at his home.
"You stood here in front of the American people and did not tell the truth that you had illegals working on your property," Perry said.
Romney responded that he was unaware that a lawn company employed illegal immigrants, and when he found out, he eventually fired the company.
For Perry, the feisty approach was an attempt to revive his campaign after stumbles in previous debates caused his poll numbers to drop.
Cain, who has overtaken Perry in the polls to join Romney at the top, came under sharp attack for his "9-9-9" tax reform plan that would establish flat 9% rates for corporate and income taxes while establishing a new 9% national sales tax.
He denied a Tax Policy Center report cited by Santorum that the plan would raise taxes for 84% of Americans, and had trouble answering Romney's insistence that the 9% sales tax would be on top of sales taxes already charged by states.
Cain argued that the state and national sales taxes were "apples and oranges" and therefore should not be compared or considered together, Romney shot back: "Fine. And I'm going to be getting a bushel basket that has apples and oranges in it because I've got to pay both taxes."