The Democratic presidential debate in South Carolina may reshape the party’s primary when it comes to national security, casting Senator Clinton and Governor Richardson as the hawks in the race, positioning Senator Obama and John Edwards in the middle, and giving new prominence to two strident opponents of military force: Rep. Dennis Kucinich and a former senator from Alaska, Michael Gravel.

Mrs. Clinton positioned herself as more willing than Messrs. Obama or Edwards, her chief rivals for the nomination, to use military force in the event of terrorist attacks against America.

“I think a president must move as swiftly as is prudent to retaliate,” Mrs. Clinton said when asked how she would use the military if terrorists struck two American cities simultaneously. The answer came in stark contrast to the responses given by Messrs. Obama and Edwards to the same question.

Mr. Obama, a first-term Illinois senator, did not address the military question at first, focusing on emergency response and diplomacy. Mr. Edwards, a former North Carolina senator, said he would act “swiftly and strongly” to hold the perpetrators responsible, but he cautioned: “We have more tools available to us than bombs.”

Mr. Richardson, the governor of New Mexico, was not asked the question but later forced his way into the issue by saying, in response to an unrelated question, that he would respond with aggressive military force if such an event occurred.

The answers were striking in an eight-candidate debate — the first face-to-face exchange of the presidential campaign — that was dominated at times by the Iraq war. The leading candidates have all advocated the withdrawal of American troops, but the inclusion in the debate of Messrs. Kucinich and Gravel, who are essentially pacifists, made the other candidates appear closer to the political center on the broader issues of national security and foreign policy. Mr. Gravel, a 76-year-old who is unknown to most voters, virtually stole the show with a series of impassioned anti-war denunciations of the rest of the Democratic field. “Understand that this war was lost the day that George Bush invaded Iraq on a fraudulent basis,” he said in his first words of the debate. He said he was “embarrassed” by the Democratic Congress, which he said was not being aggressive enough in confronting President Bush and forcing the removal of troops from Iraq.

Mr. Obama later tussled with Mr. Kucinich on policy toward Iran. The Ohio congressman accused Mr. Obama of “setting the stage for another war” with Iran when Mr. Obama said he supported the combination of strategic use of military force against terrorism with an effort to rebuild relations with the international community.

The Illinois senator took exception to that, insisting “I’m not planning to nuke anybody right now,” but he did not back down. “I think it would be a profound mistake to initiate a war with Iran, but have no doubt: Iran possessing nuclear weapons will be a major threat to us, and to the region,” he said.

The debate also had its share of lighter moments, particularly in regard to a $400 hair cut that Mr. Edwards recently paid for with campaign funds. He said it was a mistake, but Mr. Richardson used the incident to take a swipe at him. The American people, he said at one point, “don’t want blow-dried candidates with perfection.”

The New Mexico governor and former U.N. ambassador was put on the defensive himself, as moderator Brian Williams of NBC News pressed him on his acknowledgment that he had waited to call for the resignation of embattled Attorney General Gonzales because of their shared Hispanic heritage. “That’s how I felt,” Mr. Richardson said. He said that the American people “want candor” before referencing Mr. Edwards’ hair cut.

Mrs. Clinton appeared to make no major mistakes, and she repeatedly targeted the Bush administration rather than her Democratic opponents. At one point she assailed its culture of “corruption and cronyism,” signaling that the fact that such charges were leveled against her husband’s administration would not prevent her from attacking on the issue.

The candidates gathered at the historically black South Carolina State University in a state that is expected to play a crucial role in the nominating process early next year as the first primary in the South. The two front-runners, Mrs. Clinton and Mr. Obama, have been battling for support among black voters, but it is Mr. Edwards who was born in South Carolina and who won the state’s primary in 2004.

Last night’s forum, broadcast live on MSNBC, was the first to feature all the Democratic candidates on the same stage at once. It gave a virtually unknown candidate like Mr. Gravel a rare chance to reach a national audience, but the sheer number of contenders provided little opportunity to exchange in extended, substantive debate. “Debate is a misnomer,” a Quinnipiac University pollster, Peter Brown, said. “It’s very difficult for anyone in a field of eight to stand out.”

More Democratic debates are planned in the nine months leading up to the first primaries and caucuses. The first Republican face-to-face debate, featuring 10 candidates, is scheduled for May 3 at the Ronald Reagan Presidential Library in Simi Valley, Calif.