The two Democrats and Republicans Mike Huckabee and Ron Paul joined in a youth-oriented forum sponsored by MTV, The Associated Press and MySpace, each fielding questions separately by satellite.
In perhaps a sign of Obama's strength with young people, both Clinton and Huckabee were asked not just about themselves, but about him.
Clinton, asked what Obama symbolized in the contest, said she and her rival together "represent such a sea change in America" - one bidding to become the first female president, the other wanting to be the first black president. "Whichever of us gets the nomination, we are making history," she said, before rapidly asserting she is the best equipped to lead.
Equally mindful of history, Obama declared the contest is not about the race or the sex of the candidates. If it were just about his race, he said, "I wouldn't have to answer questions. I could just show up."
Clinton was in Tucson, Ariz., and Obama in Minneapolis, each in motion across a vast landscape in the closing stretch before the two dozen presidential nomination contests Tuesday. John McCain and Mitt Romney, top contenders for the GOP nomination, declined to participate in the forum.
Obama, an Illinois senator, asked young voters concerned about America's place in the world to judge him on his record of standing against the Iraq war and on his background as the son of a Kenyan father and mother from Kansas. He noted his schooldays in Indonesia.
"If I convene a meeting of Muslim leaders to try to bridge the divide between Islam and the West, I do so with the credibility of someone who lived in a Muslim country for four years when I was a child," he said. "And although I'm a Christian I have a sense of that culture."
Clinton, a New York senator, emphasized college affordability in response to a question, and outlined her proposals to help students pay off debt with national service, to increase Pell grants and to sweeten other college aid.
She said student loan companies should be cut out of the process and colleges should enter contracts with freshmen ensuring no tuition increases until they graduate.
"We are literally slamming the door of college in the face of so many young people," she said. Obama, too, talked about his national service plan to relieve college debt.
Huckabee, opening the forum, complained that he always gets "the God questions" when he'd rather be talking about public policy, and denied there's any conflict between his faith and the right things to do as president.
The former Baptist preacher was asked almost right off if he would be capable of making decisions in the Oval Office that might be at odds with his religion.
"There's not this glaring conflict," he said. "Faith helps me to understand what is right."
Religious conservatives have provided much of Huckabee's support and he's not been shy about courting them.
"I always get asked the God questions," he said, adding that "it's really been frustrating" that people don't want to know more about his work as Arkansas governor.
Paul told the forum he opposed U.S. intervention in Sudan's Darfur region and placed little faith in the ability of the United Nations to relieve the crisis there. He was asked what he'd do to stop the crisis from turning into a genocide on the scale of that experienced in Rwanda.
"I don't believe in using force in that manner," he said.
"Under the Constitution, we're not allowed to do that."
He said he might support some interim aid, steered through international agencies, to address "these social problems in Africa." The U.N. estimates that 200,000 people have died and 2.5 million have been displaced since ethnic African rebels in Darfur took up arms against the Arab-dominated central government, accusing it of discrimination, in 2003 Huckabee spoke from Montgomery, Ala., and Paul from Victoria, Texas.
