Republican presidential hopefuls tore into former Bay State Gov. Mitt Romney last night, using a Boston Herald column to blast the signature Massachusetts health-care plan he signed into law during a fiery Las Vegas showdown that offered the toughest test the top-tier candidate has faced to date.

Former U.S. House Speaker Newt Gingrich cited a column that ran in the Boston Herald yesterday as proof that Romney’s health-care reform — so-called Romneycare — is costly and flawed.

“Your plan essentially is one more big-government, high-class system,” Gingrich said. “The state of Massachusetts is fining a local small business $3,000 because a $750-a-month insurance plan isn’t adequate, according to the bureaucrats in Boston.”

Romney, who has breezed through seven earlier debates largely unchallenged, shot back that he got the idea for an individual health-care mandate from Gingrich.

“What we did was right for our state, according to the people in our state,” Romney said. He has promised to repeal President Obama’s federal health-care reform if elected.

Romney was frequently on the ropes after attacks from other rivals such as Texas Gov. Rick Perry and former U.S. Sen. Rick Santorum of Pennsylvania — who often spoke over him — as Romney struggled to answer their heated questions.

“Rick, you had your chance, let me speak,” said a rattled Romney as he responded to questions about his stand on health care and immigration. But Romney, who clashed repeatedly with a seemingly reinvigorated Perry, had a chance to swing back at the Texan and tweak him on previous poor debate showings.

“This has been a tough couple of debates for Rick and I understand that, so you’re going to get testy,” he joked.

Perry and Herman Cain, who have jousted with Romney for front-runner status, knocked Romney slightly off his game, challenging his electability. Cain, former CEO of Godfather’s Pizza, told the audience “(Romney’s) business executive experience has been more Wall Street oriented, mine has been more Main Street.”

Candidates also fired at Cain, in a virtual dead heat with Romney, according to Monday’s CNN poll. U.S. Rep. Michele Bachmann (R-Minn.) criticized his catchy 9-9-9 tax overhaul plan as “a tax plan and not a jobs plan.”

Cain defended the proposal to replace the current tax code with a new 9 percent national sales tax and a 9 percent tax on personal income and corporations.

The debate, hosted by CNN and Western Republican Leadership Conference, is the eighth in a presidential election cycle that’s been unusually influenced by the showdowns.