SIMI VALLEY, Calif. - Republican presidential candidates last night were united in offering staunch support for President Bush's troop-surge policy in Iraq as they met for their first debate of the 2008 campaign, while former New York Mayor Rudy Giuliani's comments on abortion stood apart from the other candidates'.

In the opening minutes of the debate at the Ronald Reagan Presidential Library, the 10 candidates competed with one another to identify with the former president, citing his foreign and domestic policies as models for what the Republican Party should embrace in the coming election.

The freewheeling debate initially focused on the pessimism across the country surrounding the war, and the candidates did not shrink from embracing Bush's policy.

"We must win in Iraq," Arizona Sen. John McCain said. "If we withdraw, there will be chaos; there will be genocide; and they will follow us home."

"We should never retreat in the face of terrorism," Giuliani said. "Terrible mistake."

Former Massachusetts Gov. Mitt Romney argued against following polls that show that a majority of Americans believe the war cannot be won.

"I want to get our troops home as soon as I possibly can," Romney said. "But, at the same time, I recognize we don't want to bring them out in such a precipitous way that we cause a circumstance that would require us to come back."

Bush came under criticism for his administration's management of the war, with former Arkansas Gov. Mike Huckabee saying he would have fired Donald H. Rumsfeld as defense secretary before the 2006 elections.

"Clearly there was a real error in judgment," he said, "and that primarily had to do with listening to a lot of folks who were civilians in suits and silk ties and not listening enough to the generals with mud and blood on their boots and medals on their chest."

The candidates also offered tough talk on Iran, warning against allowing the Iranians to acquire nuclear weapons and describing Iran as the greatest threat to peace. They also vowed to pursue Osama bin Laden.

"I will follow him to the gates of hell," McCain said.

The debate quickly turned to social issues.

On abortion, Giuliani's views stood in contrast from the rest of the GOP field. All the others said they would be happy if the Supreme Court overturned Roe v. Wade, which legalized abortion in 1973. Giuliani said it would be "OK" if the court did so but said it was also possible for a strict-constructionist justice to support precedent and uphold the decision.

Giuliani came under criticism for his position in support of abortion rights. When asked to explain his position, he said, "I hate abortion," but added that because the issue is one of conscience, "I would respect a woman's right to make a different choice."

Yesterday's debate included 10 announced candidates. In addition to McCain, Giuliani, Romney and Huckabee, Sen. Sam Brownback of Kansas, former Wisconsin Gov. Tommy Thompson, former Virginia Gov. James Gilmore, and Reps. Duncan Hunter of California, Tom Tancredo of Colorado, and Ron Paul of Texas participated.

The Reagan library served as host of the debate, with the former president's widow, Nancy Reagan, in the front row of the audience. The event was cosponsored by MSNBC and the Politico, a new politically oriented online site.

Although the stage was crowded with candidates, the GOP field might not be set. Former Sen. Fred Thompson of Tennessee is exploring a candidacy, and, former House Speaker Newt Gingrich of Georgia has said he might become a candidate late in the year.

The war in Iraq presents the biggest challenge to the Republican candidates. Bush's war policies are despised by most Democrats and by many independents, who could be the key to victory in November 2008. But Bush's decision to add troops in Baghdad enjoys broad support among the GOP rank and file, who will pick the Republican nominee next year.

All the candidates except Paul say that the buildup is necessary and must be given a chance to succeed.

See Dick Polman's take on the GOP debate via