Twice invoking the New Deal inventiveness of Franklin D. Roosevelt, Bill Bradley mounted an aggressive defense today of his openness to experiments with public subsidies for private schools.

Public school teachers, who in the main fiercely oppose vouchers, are expected to be the second-largest group of participants, after retirees, in the Iowa caucuses on Jan. 24, according to Democratic officials.

So Bradley, who often says that he tells people what he believes and not what they want to hear, is living up to that promise with his position on vouchers, which would help parents to pay tuition for private or parochial schools.

"I'm running under the radical premise that you can go out and tell people what you believe--and win," Bradley told 400 workers and executives this morning in the auditorium of the Principal Financial Group, which administers retirement programs.

His rival for the Democratic presidential nomination, Vice President Gore, opposes vouchers. Bradley, who voted for such experiments when he was a Democratic senator from New Jersey, made a rare deviation from his stump speech today to offer a rationale for greater choice for parents.

"I believe that every child deserves a quality education, not just the children of parents who are wealthy," Bradley said. "Honest leadership should be willing to try new and innovative ways to achieve this end.

"When FDR was the president of the United States during the Depression, he said, 'I'm going to try this, and I'm going to try that, and if it doesn't work, I'm going to try something else, but we're going to get out of this Depression.' "

Bradley invoked Roosevelt for a second time this afternoon when he was asked at a news conference about his expertise on farm issues.

"In terms of understanding the family farm, or understanding agriculture generally, that's what they used to say about FDR," Bradley said. "But then he found somebody named Henry Wallace, who helped him understand what was important in agriculture. . . . I believe I'd be the president of all the people, and that includes being an effective president for agriculture."

Jolene M. Franken, president of the Iowa State Education Association, which represents 32,000 teachers and aides, said she came away concerned about Bradley's stand on vouchers after meeting with him for an hour in October.

"After screaming and yelling and ranting and raving, I finally got a meeting with him," Franken said.

Bradley, who took an unequivocal position on vouchers today, has wavered in the past. On Sunday, during a debate with Gore on NBC's "Meet the Press," Bradley was asked if he would support tuition tax credits and vouchers as president.

"The answer . . . is no," Bradley said. But he defended voucher experiments. "If those experiments demonstrated that the quality of public education was improved because of the competition, I think that it would be very difficult to turn your back on that evidence," he said.

Gore responded that most communities are willing to spend only a set amount of money on education. "If you drain the money away from the public schools for private vouchers, then that hurts the public schools," he said at the debate.

Early in his campaign, Bradley said he did not plan to present an education platform, because he said schools were not a primary federal responsibility. This fall, he made plans for a formal education speech, like his addresses on gun control, health care and child poverty. Now that is on hold. Bradley's spokesman, Eric Hauser, said it is uncertain if Bradley will give an education speech, but Hauser said Bradley has "laid out a plan that is quite broad and thorough" by lacing it through other parts of his domestic agenda.

Bradley's education plans include a program of scholarships and loan forgiveness that would train 60,000 new teachers each year for urban and rural school districts, learning opportunities for current teachers, public-private partnerships to provide care for preschool children, incentives for senior citizens to serve as mentors for young people, and creation of a network of after-school centers run by community groups and faith-based organizations.

As Bradley was invoking Franklin Roosevelt, Gore invoked Abraham Lincoln in renewing his request that Bradley join him in stopping campaign commercials and debate regularly instead.

As he did Sunday on NBC, Bradley rejected the proposal. Spokesman Hauser called the debate proposal a "contrived gimmick" that indicated Gore's "lack of confidence in his own vision for America."

Gore issued a statement quoting an 1858 letter in which Abraham Lincoln challenged Stephen Douglas to a series of debates in their campaign for a Senate seat from Illinois. The two held seven debates. Douglas won the Senate election, but two years later Lincoln was elected president.