Romney says he may release tax returns in April MYRTLE BEACH, S.C. (AP) - Under pressure, Republican presidential candidate Mitt Romney says he might be willing to release his tax returns. But not until April, if then, and the multimillionaire former businessman is not getting much gratitude from his rivals for his grudging change of heart. "If there's nothing there, why is he waiting till April?" former House Speaker Newt Gingrich told reporters. Romney seemed hesitant when confronted about the tax returns in a Republican debate Monday night, first sidestepping calls from his rivals to release his records, then acknowledging later that he'd follow the lead of previous presidential candidates. "I sort of feel like we're showing a lot of exposure at this point," he added. Romney, the clear front-runner for the GOP nomination after back-to-back wins in the Iowa caucuses and the New Hampshire primary, was under fire from Gingrich and fellow GOP rivals Rick Perry, Ron Paul and Rick Santorum in Monday night's debate as they sought to knock him off stride. The five will meet again in debate in Charleston Thursday night, the last time they will share a stage before Saturday's South Carolina primary. The first Southern primary could prove decisive in the volatile contest. Gingrich has virtually conceded that a victory for Romney in South Carolina would assure his nomination as Democratic President Barack Obama's Republican rival in the fall, and none of the other remaining contenders has challenged that conclusion. That only elevated the stakes for Monday night's debate. It was feisty from the outset, with the attacks on Romney often couched in anti-Obama rhetoric. Texas Rep. Ron Paul won that competition handily, saying he thought the top personal tax rate should be zero. In South Carolina, a state with a heavy military presence, the tone turned muscular at times. Perry also won favor from the crowd when he said the Obama administration had overreacted in its criticism of the Marines who were videotaped urinating on the corpses of Taliban fighters in Afghanistan. Gingrich and Perry led the assault against Romney's record at Bain Capital, a private equity firm that bought companies and sought to remake them into more competitive enterprises, with uneven results. Romney said the steel industry was battered by unfair competition from China. As for other firms, he said, "Four of the companies that we invested in ... ended up today having some 120,000 jobs." And he acknowledged, "Some of the businesses we invested in were not successful and lost jobs." It was Perry who challenged Romney to release his income tax returns. The Texas governor said he has already done so, and Gingrich has said he will do likewise later in the week. We need to know now," Perry said. His response meandered. "If that's been the tradition I'm not opposed to doing that," Romney said. But I anticipate that most likely I'm going to get asked to do that in the April time period and I'll keep that open. Prodded again, he said, "If I become our nominee ... what's happened in history is people have released them in about April of the coming year, and that's probably what I'd do." April is long after the South Carolina primary and the Republican nomination could easily be all but decided by then, following Super Tuesday contests around the country in March. Santorum stayed away from the clash over taxes, instead launching a dispute of his own. Santorum instantly said that as governor of Massachusetts, Romney hadn't made any attempt to change a law that permitted convicted felons to vote while still on parole, a law the former Pennsylvania senator said was more liberal than the one he has been assailed for supporting. Romney replied that as a Republican governor, he was confronted with a legislature that was heavily Democratic and held a different position. "It is inaccurate," Santorum said of the ad assailing him. I would go out and say: `Stop it. That issue returned more than an hour later, when Gingrich said he too has faced false attacks from the same group that is criticizing Santorum. He noted that Romney says he lacks sway over the group, "which makes you wonder how much influence he would have if he were president." Romney said he hoped no group would run inaccurate ads, and he said the organization backing Gingrich was airing a commercial that is so false that "it's probably the biggest hoax since Bigfoot." He called for scuttling the current system of campaign finance laws to permit individuals to donate as much money as they want to the candidates of their choice. Noting that the debate was occurring on Martin Luther King Jr. Day, one moderator asked Gingrich if his previous statements about poor children lacking a work ethic were "insulting to all Americans, but particularly to black Americans." "No," Gingrich said emphatically, adding his aim was to break dependence on government programs. "I'm going to continue to find ways to help poor people learn how to get a job, learn to get a better job and learn someday to own the job," he said. Romney is the leader in the public opinion polls in South Carolina, although his rivals hope the state's 9.9 percent unemployment rate and the presence of large numbers of socially conservative evangelical voters will allow one of them to slip by him. Associated Press writer Dave Espo contributed to this report. 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