COLUMBIA, S.C. - Under pressure from their rivals, the leading Republican presidential contenders defended their conservative credentials last night on abortion, gun control and tax cuts.

"I ultimately do believe in a woman's right of choice, but I think there are ways we can look for ways to reduce abortions," former New York Mayor Rudy Giuliani said during the second Republican debate of the campaign.

Former Massachusetts Gov. Mitt Romney said he had signed legislation banning assault weapons but added that he supported the rights of gun owners under the Second Amendment.

Arizona Sen. John McCain said he would make sure that President Bush's tax cuts were made permanent, even though he voted against them when they were passed in 2001.

He said he had done so because they were not accompanied by spending cuts.

All three men sought to stand their ground - and protect their standing in the presidential race - in the 90-minute debate at the University of South Carolina.

In a break from the campaign's first debate, some of the contenders who lag in the polls jabbed sharply at the front-runners.

Asked whether he believed that 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," Tancredo 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.

Gimore 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 had raised taxes in response to a court order. He said he had cut taxes repeatedly.

On defense for much of the evening, Giuliani switched gears nearly an hour into the debate, challenging Texas Rep. Ron Paul's suggestion that the U.S. bombing of Iraq had contributed to the Sept. 11, 2001, terrorist attacks.

As someone who lived through 9/11, the man who was New York mayor at the time, 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 audience.

There were a few moments when the Republicans sought to turn the campaign spotlight on the Democrats, who are seeking to win back the White House after President Bush's two terms.

"We've had a Congress that's spent money like John Edwards at a beauty shop," Mike Huckabee said, mocking the Democratic presidential hopeful's $400 haircut.

Huckabee did not mention that until January, Congress was under the control of Republicans for a dozen years.

Giuliani criticized the Democratic front-runner, New York Sen. Hillary Rodham Clinton, at one point, in response to a question about abortion. That prompted one of the debate moderators, Chris Wallace of Fox, to ask whether the former mayor would answer the question.