While the candidates differed somewhat over the level of threat Iran poses in the Mideast, most of them sought to liken the administration's approach to Iran with its buildup to the war in Iraq.
"I vehemently disagree with the president that nothing's changed and therefore nothing in American policy has to change," said New York Sen. Hillary Rodham Clinton. "We do know that pressure on Iran does have an effect. I think that is an important lesson."
Delaware Sen. Joseph R. Biden Jr., chairman of the Senate Foreign Relations Committee, said the new intelligence report indicated that Iran dropped its program before international pressure came into play.
"It was like watching a rerun of his statements on Iraq five years earlier," Biden said. "Iran is not a nuclear threat to the United States of America. Iran should be dealt with directly, with the rest of the world at our side. But we've made it more difficult now, because who is going to trust us?"
The debate was aired without a studio audience over NPR, live from the Iowa State Historical Museum. It covered Iran, China and immigration, offering the contenders a chance to delve more deeply into subjects that often receive less detailed debate treatment.
Clinton and Biden were joined by Illinois Sen. Barack Obama, former North Carolina Sen. John Edwards, Connecticut Sen. Christopher J. Dodd, Ohio Rep. Dennis J. Kucinich, and former Alaska Sen. Mike Gravel.
New Mexico Gov. Bill Richardson missed the debate to attend the funeral of Cpl. Clem Robert Boody in Independence, Iowa. Boody was a Korean War soldier whose remains Richardson had helped retrieve from North Korea earlier this year.
The National Intelligence Assessment report on Iran, released Monday, was the focus of the first third of the two-hour debate.
The assessment concluded that Iran halted its nuclear program in 2003 largely because of international pressure -- reversing a conclusion made two years ago that the nation was aggressively pursuing nuclear weapons.
The Democrats used the issue to criticize each other as well as President Bush. Yet their own prescriptions for dealing with Iran are similar -- and fairly close to the administration's approach of increasing diplomatic and economic pressure to force Tehran to suspend enriching uranium that can be used for making nuclear weapons.
The leading Democratic candidates have differed over whether to negotiate directly with Iran. In a July debate, Obama said he would be willing to meet with Iranian President Mahmoud Ahmadinejad, a position criticized by Clinton and others. But front-runners Clinton, Obama and Edwards have all said they would not rule out military action against Iran.
For their part, Republican candidates have said that the new intelligence estimate did not change their view of Iran as a major threat to the United States -- a view also held by Bush.
In the Democrats' debate Tuesday, the focus on foreign-policy issues gave Clinton a chance to bring up what many people believe was the high point of her eight years as first lady -- her speech at the 1995 U.N. Fourth World Conference on Women in Beijing. In it, she castigated China over its treatment of women, arguing that women's rights could no longer be considered separate from human rights. The Chinese government blocked the speech from being heard within China.
As at the Black & Brown Forum here Saturday night, the debate did not provide any landscape-shifting moments. Exchanges among the candidates were polite -- but also at times direct, particularly over the recent bill sponsored by Sens. Jon Kyl (R-Ariz.) and Joe Lieberman (I-Conn.) that unofficially declared the Iranian Revolutionary Guard a terrorist organization.
Clinton was the only Democratic candidate to vote for the bill. When asked whether she thought the Revolutionary Guard were "proliferators of mass destruction," she said "many of us believe that" and suggested that earlier comments by Obama and Edwards about Iran indicated that they did too.
Edwards and Obama responded that they believed Iran was a threat to stability in the Mideast but that the administration was moving toward an unnecessary war.
"What I believe is that this president, who, just a few weeks ago, was talking about World War III, he, the vice president, the neocons have been on a march to possible war with Iran for a long time," Edwards said. "We know that they've prepared contingency plans for a military attack."
Obama, who missed the Kyl-Lieberman vote in the Senate because he was campaigning in New Hampshire, also drew parallels to the Iraq war buildup.
"What I've been consistent about was that this saber-rattling was a repetition of Iraq, a war I opposed, and that we needed to oppose George Bush again," Obama said. "We can't keep on giving him the benefit of the doubt, knowing the ways in which they manipulate intelligence."
Kucinich, who has been a vocal opponent of the war in Iraq since before it began, accused his rivals of embracing the use of military action where it was unwarranted.
"When people say all options are on the table, as the three senators have, they actually encouraged President Bush and licensed his rhetoric," Kucinich said. "What I'm saying is that I'm the only one here who in Congress repeatedly challenge, in every chance and every legislation, repeatedly challenge this mindset that said all options are on the table and that Iran had nuclear weapons programs."
A discussion of product safety and China provided the debate's lightest moment, when NPR moderator Michele Norris asked Edwards whether he would buy his two young children toys made in China as Christmas presents this year. "No, ma'am, I will not," he replied.
Fellow moderator Robert Siegel said Dodd deserved "equal time on that." Dodd replied that he and Obama -- who, like Edwards, have two children under age 10 -- "would like to comment on this. My toys are coming from Iowa. I'm buying Iowa toys."
Times staff writer Doyle McManus in Washington contributed to this report.