GOP debate focuses on negative tone MYRTLE BEACH, S.C., Jan. 16 (UPI) -- Monday's presidential candidates' debate in South Carolina focused on the negative tone of the campaign, particularly regarding Mitt Romney's business record. With the field of GOP hopefuls narrowed down to five following the departure of former Utah Gov. Jon Huntsman, the remaining candidates gathered in Myrtle Beach for a debate televised live by Fox News Channel. The first question was directed at former U.S. House Speaker Newt Gingrich, who was asked to defend recent attacks on Romney's background as a venture capitalist. Gingrich and Texas Gov. Rick Perry, as well as a so-called super PAC that supports Gingrich, have criticized Bain Capital LLC for taking over and eventually closing distressed companies, while realizing multimillion dollar profits -- but the criticism has resulted in a backlash from defenders of Bain's business practices, who see the attacks as directed at the free enterprise system. "I raised questions that I think are legitimate questions," Gingrich said. He said explaining his business practices was "part of (Romney's) responsibility as a candidate." Perry called on Romney to release his tax returns "so the people of this country can see how you made your money" and "decide whether we've got a flawed candidate or not." Romney said later in the debate he would "probably" released his tax returns in April. "I hadn't planned on releasing tax records but you know if that's been the tradition I'm not opposed to doing that," he said. I'm happy to do so. Huntsman announced Monday he had suspended his campaign for president and supports Romney for the Republican nomination. Huntsman, the former governor of Utah and ambassador to China -- appointed by President Barack Obama -- skipped the Iowa caucuses, banking on a strong showing in last week's New Hampshire primary.