Iran, rather than Iraq, dominated the foreign policy segment of Tuesday night's Democratic presidential candidates' debate, with competitors pouncing on Hillary Clinton for her stance on the nuclear challenge posed by the Islamic Republic. Former vice presidential nominee John Edwards led the attack on the New York senator, arguing that she was enabling bellicosity by the Bush administration in its handling of Iran. He and others pointed to her recent vote in favor of a nonbinding sense of the Senate amendment calling on the US to designate Teheran's Revolutionary Guard Corps a foreign terrorist organization. That move, which received the support of 76 out of 100 senators, has been criticized as paving the way to war. Clinton defended her vote as bolstering diplomacy rather than military confrontation. "Some may want a false choice between rushing to war, which is the way the Republicans sound - it's not even a question of whether, it's a question of when and what weapons to use - and doing nothing," she said. Later, she stressed, "We shouldn't be doing nothing, and that means we should not let them acquire nuclear weapons. And the best way to prevent that is a full court press on the diplomatic front." At one point, Edwards lambasted Clinton for voting in favor of "a resolution that looks like it was written, literally, by the neo-cons." He said the amendment "gave Bush and Cheney exactly what they wanted" and that they then "acted on it," with their designation last week of the Revolutionary Guards as a weapons proliferators and its Quds Force off-shoot as helping terrorist organizations. Illinois Sen. Barack Obama said the sense of the Senate amendment "doesn't send the right signal to our allies or our enemies. And, as a consequence, I think over the long term, it weakens our capacity to influence Iran." He pushed further attempts at diplomacy, but said in response to a question about what his red line for attacking Iran would be that "there may come a point where those measures have been exhausted and Iran is on the verge of obtaining a nuclear weapon, where we have to consider other options. But we shouldn't talk about those options now, when we haven't even tried what would be a much more effective approach." When Clinton was asked if she would pledge that Teheran would not acquire nuclear weapons during her presidency, she said, "I intend to do everything I can to prevent Iran from developing a nuclear bomb." Edwards, asked the same question, said he would "take all the responsible steps that can be taken to keep Iran from developing a nuclear weapon." With the first primaries for January, those trailing Clinton in the race for the nomination have turned up the heat. Tuesday night's debate, broadcast on MSNBC, featured a notable shift in temperature, as Clinton's competitors went after her more frequently and more directly than they have in other forums. Iran was one of the initial vehicles for the attack, and it became the central issue for the first third of the debate. And it was used by Republican candidate Rudy Giuliani to put down Democrats before the debate even began. On a campaign stop Monday in New Hampshire, scene of the first primary, Giuliani criticized Clinton and Obama for saying they would engage in diplomacy with Iran. Obama has said he would be willing to meet with Iran's leader in the first year of his presidency without conditions; Clinton has said envoys below the presidential level should begin diplomatic work. "This is the world we live in. It's not this happy, romantic-like world where we'll negotiate with this one, or we'll negotiate with that one and there will be no preconditions, and we'll invite [Iranian President Mahmoud] Ahmadinejad to the White House, we'll invite Osama [bin Laden] to the White House," Giuliani said. "Hillary and Obama are kind of debating whether to invite them to the inauguration or the inaugural ball," he cracked. Amid the political parrying, a Zogby poll released this week showed a slim majority of the American public would support an attack to prevent Iran from building a nuclear weapon. Some 52 percent said they were either somewhat or very supportive, while close to 42% said they were not very or not at all supportive. The poll of 1,028 likely voters has a 3 percentage points margin of error. Clinton was chosen as the best equipped to deal with Iran (20.5%), leading Giuliani (next with 14.7%), McCain (14.3%), Obama (10.4%) and all the rest of the candidates. AP contributed to this report.