Greenville, South Carolina (CNN) – Republican presidential candidate Newt Gingrich defended his professional record and embraced being labeled a "lifelong politician" by frontrunner rival Mitt Romney Wednesday.
"You know, I haven't been as successful as Mitt Romney," said Gingrich. "I've had a long work record in many different jobs and some of them have been really profitable and some of them didn't pay much."
Speaking to reporters at Tommy's Country Ham House, Gingrich pointed to babysitting at Fort Riley in Kansas and being a pinsetter at a bowling alley as low-paying jobs he held in his early teens.
Gingrich mentioned being a small business owner but the White House hopeful but did not mention the lucrative paid speaking circuit or the millions of dollars he earned from clients that included mortgage giant Freddie Mac, after serving for decades as a top House Republican.
Romney's critique of the former House Speaker comes after Gingrich took a swipe at the former Massachusetts governor's conservative record. The exchange follows a recent shift in the GOP presidential race, pitting the two candidates in a heated competition for the top spot in national polls.
Gingrich dismissed the notion that Romney was attacking him. "People get to do what they want to do. I'm going to stay positive," he said.
That didn't stop him from calling fellow presidential contender Michele Bachmann "factually challenged" and likening her to a misguided student.
"It's unfortunate. In the eyes of a teacher, occasionally I'd have a student who couldn't figure out where things were or what things were or what the right date was. When that happens you feel sorry that they're so factually challenged," said Gingrich.
Gingrich was chiding the Minnesota congresswoman for distorting his position on illegal immigration saying Gingrich favors amnesty for the estimated 11 million immigrants living illegally in the United States. He added, "What I will say is voters will be pretty good over time at distinguishing between people who know the facts and people who don't know the facts."
Wrapping up a three-day campaign swing through the early southern primary state, Gingrich would not speculate whether his campaign might benefit if businessman Herman Cain ended his presidential campaign.
"I don't think you think in those kind of calculus at this point. He's got to do what he thinks is right. All the different candidates will do whatever they do in response to his decision," he said.
– Follow Shawna Shepherd on Twitter: @ShepherdCNN.