May 16 (Bloomberg) -- Rudy Giuliani seized an opportunity to burnish his tough-on-terrorism credentials last night while his top two rivals for the Republican presidential nomination, John McCain and Mitt Romney, attacked each other on immigration and abortion.

The second debate among all 10 Republican hopefuls featured most candidates trying to define themselves as genuine conservatives on national security, terrorism, taxes, federal spending and social issues such as abortion.

Giuliani, the former mayor of New York, jumped in to object after Texas Representative Ron Paul, 71, suggested the terrorist attacks on the U.S. in 2001 were precipitated by American interventions in the Middle East.

``That's an extraordinary statement, as someone who lived through the attack of Sept. 11, that we invited the attack,'' Giuliani, 62, said during the debate in Columbia, South Carolina. ``I don't think I've ever heard that before, and I've heard some pretty absurd explanations for Sept. 11.''

Giuliani's statement, which drew applause from the crowd, came after the Republican frontrunner defended himself from attacks from some of the second-tier candidates for his support of abortion rights.

The other highlight of the debate was an exchange between Romney, the former governor of Massachusetts, and McCain, a U.S. senator from Arizona. The two squared off on immigration, with Romney saying he objected to a McCain-sponsored measure because it might give people who have been in the U.S. illegally an advantage when applying for citizenship.

Consistency

``It said people who are here illegally get a special pathway,'' Romney, 60, said. ``That's what's wrong about it.''

McCain, 70, responded by saying he's been consistent in his positions on issues from campaign finance reform to abortion. In a slap at Romney, McCain said, ``I haven't changed my position on even-numbered years or have changed because of the different offices I may be running for.''

While running for the Senate in Massachusetts in 1994 and in his successful campaign for the governorship in 2002, Romney supported a woman's right to an abortion. He said he changed his mind and is now against abortion rights.

The 90-minute debate, sponsored by Fox News and the South Carolina Republican Party, allowed candidates trailing in the polls to confront the front-runners. The second-tier candidates questioned the leading contenders on abortion and immigration and, echoing McCain's criticism of Romney, suggested some had changed positions for political expediency.

`Road to Des Moines'

``I'm glad to see conversions,'' Colorado Representative Thomas Tancredo, 61, said. ``But I must tell you, I trust those conversions when they happen on the road to Damascus, not on the road to Des Moines,'' he said, referring to the first contest in the nomination race, the Iowa caucuses next January.

Said former Virginia Governor James Gilmore, 57, ``I think that some of the people on this stage were very liberal in characterizing themselves as conservatives.''

Giuliani, the target of some of those attacks, said he ``ran the most conservative government in the last 50 years in New York City'' when asked if he was a ``true conservative.'' He and other candidates who had served as mayors or governors trumpeted their tax-cutting records.

Giuliani and McCain were in a statistical tie in a May 4-6 CNN/Opinion Research Corp. poll. Giuliani drew the support of 25 percent of registered Republicans, compared with 23 percent for McCain, a gap within the poll's margin of error of 5 percentage points. Romney came in third among declared candidates.

Little Change

In the end, the top candidates entering the night came out that way as well, said Tucker Eskew, a veteran Republican operative who isn't working for any of the candidates.

``It was a good night for the big three,'' Eskew said just after the debate ended. ``We like our leaders and tonight we saw three strong leaders.''

All of the candidates vowed to rein in spending and cut taxes. Giuliani said that as New York mayor ``I put controls on every one of the city agencies, which is what I would do in Washington.'' He promised to ``do Reagan like, across-the-board budget cuts, 5 to 20 percent.''

Giuliani said about 50 percent of federal employees are going to retire in the next 10 years and he pledged not to refill half of those positions. Romney also said he would use that turnover to reduce the government workforce and said he would go through all the agencies and departments ``and cut out the unnecessary and the wasteful.''

Targeting Democrats

The candidates also took aim at two of the top candidates for the Democratic presidential nomination.

Giuliani, saying there is something ``really big at stake'' in the election, targeted New York Senator Hillary Clinton. Giuliani said Clinton agreed with the statement ``that the unfettered free market is the most disastrous thing in modern America'' and also said that taxes are needed because ``we have to take money from you in order to give it to the common good.''

``Republicans should be uniting to make certain that what the liberal media is talking about -- our inevitable defeat -- doesn't happen,'' he said.

In a 1996 C-Span interview, Clinton said she agreed with a quote she cited her book, ``It Takes a Village,'' that ``The unfettered free market has been the most radically disruptive force in American life in the last generation.'' Clinton also said in the interview ``that the market is the driving force behind our prosperity,'' ``but that it cannot be permitted just to run roughshod over people's lives as well.''

Her comment on taxes was made to an audience in San Francisco in 2004 and referred to repealing some of President George W. Bush's income tax cuts for the richest Americans, the Associated Press reported at the time.

Clinton spokesman Phil Singer didn't immediately respond to a request for comment.

Former Arkansas Governor Mike Huckabee took a shot at former Senator John Edwards, another Democratic candidate, in making a point about government spending.

``We've had a Congress that's spent money like John Edwards at a beauty shop,'' he said, drawing the loudest laugh of the evening from the audience. Edwards last month said he reimbursed his campaign for two $400 haircuts he got in Beverly Hills, California.

To contact the reporters on this story: Kristin Jensen in Washington at kjensen@bloomberg.net; Catherine Dodge in Washington at Cdodge1@bloomberg.net.

Last Updated: May 16, 2007 00:44 EDT