Under pressure from their rivals, the leading Republican presidential contenders defended their conservative credentials on abortion, gun control and tax cuts in a feisty debate Tuesday night. "Republicans should be uniting" to defeat the Democrats, implored former New York Mayor Rudy Giuliani, rather than stressing their differences with one another. Giuliani, pressed repeatedly on his support for abortion rights, wasn't the only contender to field pointed questions. Former Massachusetts Gov. Mitt Romney conceded he had signed legislation banning assault weapons but said, "Let's get the record straight." He said he is a supporter of the rights of gun owners under the Second Amendment. Arizona Sen. John McCain (news, bio, voting record) of Arizona said he would make sure that President Bush's tax cuts are made permanent, even though he said he had voted against them because they were not accompanied by spending cuts. "If we don't make them permanent then every business farm and family will have to adjust their budgets to what is in effect a tax increase," he said. All three men sought to stand their ground - and protect their standing in the presidential race - in a 90-minute debate at the University of South Carolina. The 10 men on the debate stage differed only by degree when it came to the familiar Republican themes of tax cuts, reduced spending and a smaller federal bureaucracy. Giuliani called for "Reagan-like budget cuts across the board" of between 5 percent and 20 percent, and Tommy Thompson said he had cast many vetoes while governor of Wisconsin to hold down spending. In a change from the campaign's first debate, on May 3, some of the contenders who lag in the polls jabbed at the front-runners. Asked whether he believes McCain, Romney and Giuliani were soft on immigration, Rep. Tom Tancredo of Colorado said, "I do." That wasn't all, he added quickly, saying his rivals had undergone recent conversions on abortion and other issues. "I trust those conversions when they happen on the road to Damascus and not on the road to Des Moines," he said, contrasting the biblical with the political. Former Virginia Gov. Jim Gilmore bore in, as well. "Some of the people on this stage were very liberal in characterizing themselves as conservatives, particularly on the issues of abortion and taxes and health care," he said. He singled out Giuliani for his position on abortion and said another rival, Mike Huckabee, had raised taxes while serving as governor of Arkansas. Huckabee responded that the state raised taxes in response to a court order and said he had cut taxes repeatedly. On defense for much of the evening, Giuliani switched gears nearly an hour into the debate, challenging Rep. Ron Paul (news, bio, voting record)'s suggestion that the US bombing of Iraq had contributed to the terrorist attacks of 2001. As mayor of New York at the time of the attacks, Giuliani said sternly, "I don't think I've ever heard that before, and I have heard some pretty absurd explanations." His rebuke to Paul drew some of the loudest applause of the night from the partisan audience. McCain and Romney also sniped at one another. Romney criticized the Arizona senator for working across party lines on two bills that conservatives oppose, measures on immigration and campaign spending. In a slap at the former Massachusetts governor, McCain said: "I haven't changed my position in even-numbered years or ... because of the different offices that I may be running for." Romney, in turn, poked at McCain's call for closing the prison at Guantanamo Bay, Cuba, saying: "Some people have said we ought to close Guantanamo." However, Romney said, he would imprison even more suspected terrorists there. "I'm glad they're at Guantanamo. I don't want them on our soil," he said. There were few moments when the Republicans sought to turn the campaign spotlight on the Democrats, who are embarked on a drive to win back the White House after Bush's two terms. "We've had a Congress that's spent money like John Edwards at a beauty shop," Huckabee said, mocking the Democratic presidential hopeful's penchant for $400 haircuts. He did not mention that until January, Congress has been under the control of Republicans for a dozen years. Giuliani combined his plea to unite against the Democrats with an attack on New York Sen. Hillary Rodham Clinton as an apostle of big government. "Those are the things that we should be debating and Republicans should be uniting to make certain what the liberal media is talking about, our inevitable defeat, doesn't happen," he said. Not everyone was convinced. Rep. Duncan Hunter (news, bio, voting record), the top Republican on the House Armed Services Committee, noted his experience on military matters and challenged those on stage with him to lay out their credentials to be commander in chief.