"We should never retreat in the face of terrorism," said former New York Mayor Rudy Giuliani during the debate Thursday night. "Terrible mistake."
Sen. John McCain said the war effort was now on the right track, although he said that until recently, the war had been "terribly mismanaged" by the Bush administration. "Terribly mismanaged," he repeated for emphasis.
Former Massachusetts Gov. Mitt Romney also said the United States must support the government of Nouri al-Maliki to combat terrorists.
"I want to get our troops home as soon as we possibly can, but at the same time we don't want to get them out in such a precipitous way that we have to go back," he said, warning that too hasty a departure could lead to chaos in the region.
"They have to dance this very, very careful dance between not pushing themselves too far away from the president, because his supporters are those that they need to bring along into their camp," says CBS News political analyst Nicole Wallace.
Giuliani, McCain and Romney were the first among 10 equals on the debate stage at the Ronald Reagan Presidential Library — the men with the most money and the best approval ratings in the polls more than eight months before the first delegates for the party's 2008 national convention are picked. The presidential election is in November 2008.
Also on stage were Sen. Sam Brownback; former Govs. Mike Huckabee of Arkansas, Tommy Thompson of Wisconsin, Jim Gilmore of Virginia; and Reps. Tom Tancredo, Duncan Hunter and Ron Paul.
The opening moments of the debate dealt with Iraq, and the calls for continuing the U.S. military operation contrasted sharply with last week's debate among Democratic presidential hopefuls.
Then, eight presidential hopefuls called for an end to the military involvement that so far has claimed the lives of more than 3,300 U.S. troops.
Romney and McCain squared off over terrorist leader Osama bin Laden without directly addressing each other. Last week, the ex-governor said, "it's not worth moving heaven and earth spending billions of dollars just trying to catch one person" and advocated a broader strategy to defeat Islamic jihadists. McCain had called the comment "naive."
Under questioning, Romney defended his comment, saying: "It's more than Osama bin Laden. But he is going to pay and he will die."
McCain shot back, saying bin Laden's responsible for the deaths of thousands of innocent Americans. "We will do whatever is necessary. We will track him down. We will catch him. We will bring him to justice and I'll follow him to the gates of hell," he said.
On the sensitive topic of abortion, Giuliani said during the debate that "it would be OK" if the Supreme Court upholds a 1973 abortion rights ruling.
"It would be OK to repeal it. It would be OK also if a strict constructionist viewed it as precedent," said Giuliani, who has a record of supporting abortion rights.
His nine rivals agreed that it would be a great day if the court overturns the landmark ruling.
The issue of abortion looms large in the 2008 Republican presidential campaign as a wide swath of the party's activists support the overturning of the top U.S. court's 1973 Roe v. Wade ruling that legalized abortion in the country.
In a debate that ranged broadly, most of the contenders said they opposed legislation making federal funds available for a wider range of embryonic stem cell research.
The technique necessarily involves the destruction of a human embryo, and is opposed by many anti-abortion conservatives as a result.
There are exceptions, though, including Reagan's widow, Nancy, who was in the debate audience. Also, public opinion polls show overwhelming support for the research, which doctors say holds promise for treatment or even cures of numerous diseases.
Most of the contenders said they opposed expanded federal research.
McCain was the exception, saying unambiguously he supports expanded federal research into embryonic stem cells.
Thompson said he could not provide a yes or no answer, and Giuliani's response was open to interpretation.
He said he supports it "as long as we're not creating life in order to destroy it," then added he would back funding for research along the lines of legislation pending in Congress.
The bill he cited does not expand research on embryonic stem cells, however, but deals with adult stem cells.
The men vying to become the country's 44th president said they were the rightful successors to Reagan, the popular Republican president who died in 2004.
"John McCain has alienated social conservatives in the past. Giuliani has a very colorful personal life. Mitt Romney has flip-flopped on some issues. Accordingly, the Reagan conservatives don't feel they have a dog in the fight," Jack Pitney, professor of government at Claremont McKenna College, told CBS News correspondent Sandra Hughes.
"His philosophy was a philosophy of strength," Romney said.
Speaking of Iran, Giuliani said "they looked in Ronald Reagan's eyes and in two minutes they released the hostages." That was a reference to the U.S. hostages released from captivity on the day of Reagan's inauguration in 1981.
He didn't mention other hostages taken on Reagan's watch — those seized in Lebanon and kept for years.
MSNBC and The Politico co-sponsored the debate, moderated by MSNBC's Chris Matthews.
Missing were three Republicans still weighing whether to run — Fred Thompson, the actor and former senator; Newt Gingrich, the ex-House speaker; and Sen. Chuck Hagel. They also were not slated to participate in two more debates — in South Carolina and New Hampshire — in the next month.