Columbia, South Carolina (CNN) - South Carolina Governor Nikki Haley warned the GOP field against attacking Mitt Romney's private sector record at an enthusiastic rally for the Republican front-runner Wednesday.
"We have a real problem when we have Republicans talking like Democrats against the free market," she said as the audience cheered. "We believe in the free market."
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A former businesswoman, Haley appealed to the audience as fellow executives.
"We want companies to be able to do what is best for companies, and during tough times you downsize and you make hard decisions and during good times you expand and you help those businesses grow more," she said in her introduction to Romney. "That's what he's done. He's done what every one of us has tried to do."
Haley joined a growing chorus of Republican leaders who have voiced concerns about an increasingly bitter Republican primary race, in which Romney's career at a private equity firm has come under heated attack.
In appearances across the state this week, Texas Gov. Rick Perry has accused Romney of participating in "vulture capitalism" at Bain Capital. A super PAC supportive of Newt Gingrich has bought $1.6 million in advertising time in South Carolina to run a television spot critical of Romney's tenure at Bain, as the Republican primary shifts to the third voting contest.
Earlier in the day Romney said he was "surprised" Republicans had focused on his business career.
"I was a little surprised to see Newt Gingrich as the first witness for the prosecution but I don't think that's going to hurt my efforts," he told reporters. "Frankly if I can't take a few shots coming from my colleagues on the Republican side, I'm not ready for Barack Obama."
The audience at Romney's first South Carolina event was notably supportive, and the GOP candidate stayed for more than 30 minutes shaking hands with voters.
A CNN/TIME/ORC poll taken last week showed Romney with a commanding lead in the state, before the candidate won New Hampshire's primary.
But Romney played down his chances in the Southern state earlier Wednesday, calling his effort "an uphill battle."
"With regards to South Carolina, last time I came in fourth, so our team recognizes this is going to be a challenge," he told reporters.