Nine Republican presidential candidates shared a Des Moines stage Sunday morning in a televised debate aired nationwide on ABC, but the most memorable moment came in a candidate’s comment about a Democrat.

Former Massachusetts Governor Mitt Romney ridiculed Democratic presidential candidate Barack Obama’s recent statements about foreign policy. "I had to laugh at what I saw Barack Obama do. I mean in one week, he went from saying he’s going to sit down — you know — for tea with our enemies, but then he’s going to bomb our allies," Romney said.

The crowd and some of the other candidates began to laugh. "He’s gone from Jane Fonda to Dr. Strangelove in one week," Romney added. Near the beginning of the 90-minute-long debate, Texas Congressman Ron Paul drew cheers — and a few boos — from the invited crowd when he repeated his call for getting out of Iraq.

"We ought to just come home. The number one reason: it’s in our national self-interest…think of our defenses now and how run down they are," Paul said.

Another memorable moment came near the end of the debate when the candidates were asked to cite one mistake they’d made and how it defined their life. Former New York Mayor Rudy Giuliani brought the house down in laughter with his response.

"To have a description of my mistakes in 30 seconds?" Giuliani said. Another candidate chimed in, calling it a "great line" as the crowd laughed and applauded. Moderator George Stephanopoulos asked Giuliani for "just one defining mistake."

Giuliani responded: "George, your father is a priest. I’m going to explain it to your father, not to you." Stephanopoulos replied: "Fair enough."

Former Wisconsin Governor Tommy Thompson offered this as his "defining" mistake in life: "My mother-in-law died of breast cancer…my wife has breast cancer. My daughter has breast cancer. I don’t think I was supportive enough and that’s why I’m vowing right to end breast cancer by 2015 for all the women in America."

While Paul was the only one of the candidates to directly criticize their current Republican president, a question about Vice President Dick Cheney’s role drew some sharp responses from the candidates.

Arizona Senator John McCain began by joking that a vice president’s primary role was to check on the president’s health, but then he offered this barb at the belief that Cheney wields great influence in the Bush Administration.

"Look, I would be very careful that everybody understood that there’s only one president," McCain said.

California Congressman Duncan Hunter picked up that theme. "I would not share the role of a commander in chief with a vice president," Hunter said.  Kansas Senator Sam Brownback suggested Bush has "over-relied" on Cheney. "I think you need somebody coming into the presidency that’s had foreign policy experience…so that they don’t have to depend on the vice president as much," Brownback said.

The candidates were quizzed about their views on health care reform, and many accused Democrats of trying to install "socialized medicine" in America. "It’s not the responsibility of the federal government to provide womb to tomb health care for America," said Colorado Congressman Tom Tancredo, to applause from the crowd.

The most disagreement among the candidates came in a discussion about tax policy. Former Arkansas Governor Mike Huckabee is an advocate of the so-called "fair tax" which would get rid of most federal taxes and impose a nationwide, 23 percent sales tax instead. "What the fair tax does is it ends the underground economy," Huckabee argued. "No more illegals, no more gamblers, prostitutes, pimps and dope dealers will be able to escape the tax code."

The event was staged at Drake University, the first presidential candidate debate held in Iowa this year. In two weeks, ABC will host another debate at Drake featuring the Democratic candidates.

AUDIO: Henderson report (mp3 runs 3 min 30 sec)