The second debate between Vice President Gore and former New Jersey senator Bill Bradley underscored why their fight for the Democratic nomination has become so competitive.

Gore and Bradley had different missions tonight. Gore, his unfavorable ratings rising, had to avoid looking too negative while continuing to press his rival on the issues. Bradley, whose failure to rebut Gore's attacks in their first debate cost him politically, needed to be more assertive in responding to any assaults from the vice president, without giving up his image as an atypical politician.

Each largely accomplished what he set out to do. As a result, the second debate between the Democratic candidates may have done little more than harden the supporters already committed to each man. For the undecided, tonight's debate left a choice between sharply contrasting styles of campaigning and leadership, rather than differing positions on issues.

Gore and Bradley locked horns over health care and education, but for the most part their second debate was only slightly less civil than their first. For much of the night, ranging over terrain that included discourses about race, gay rights, and whether America should send a manned mission to Mars, they agreed more than they disagreed.

But each candidate remained cautious in approach. Neither appeared willing to take a risk tonight to change the dynamic of a contest that in New Hampshire remains a largely even race.

It was left to ABC's Ted Koppel, the moderator for the special "Nightline" town meeting, to ask a final question of the two. Koppel said even he was having trouble seeing big policy differences between the two. Instead, he asked the two rivals to describe to the viewers why each thought he would make a better president.

Bradley, who has needled the vice president throughout the year for timidity and lack of vision, said he had always tackled big problems regardless of the political risk. "As president, I would continue to take those bold positions."

Gore, whose campaign has been by far the more aggressive, said he is a fighter. "For 23 years, I have fought for working families, for working men and women." But he could not resist a dig of his own. "He's a good man with bad plans," he said of Bradley.

Those answers not only illuminated their individual self-images, but reinforced their appeal to different elements of the Democratic Party.

Gore the fighter has found greater support among traditional Democrats--blue-collar workers, union laborers and traditional party constituencies. Bradley the sometime philosopher has found a base among the affluent, the well educated and those in the party's liberal wing.

The test over the next six weeks, as the two men compete in Iowa and New Hampshire, will be how successful each is at enlarging his base of support, and which candidate can reach beyond where he now stands.

This was a different Bradley than the one who debated in Hanover, N.H., at the end of October. That night he appeared reluctant to engage his opponent. Tonight he was tuned up to respond immediately.

When Gore claimed that he, like Bradley, supports universal health care, Bradley shot back that the vice president had proposed no such thing. "Who would you leave out?" he asked Gore.

When Gore said Bradley had not proposed a significant education plan, Bradley responded that the vice president's staff had not done a very good job of examining what Bradley has had to say on the campaign trail. He then claimed educational improvements are part of most of the big issues he talks about--although Gore is essentially correct that Bradley has not made education a centerpiece of his campaign.

Gore used the first debate to launch a series of attacks against Bradley that have become progressively sharper by the week. But tonight he did not do what some Democrats expected. While pointed in his criticism of Bradley, particularly on health care, he never taunted his opponent, nor did he appear sarcastic as he sometimes has in recent weeks.

Gore challenged Bradley most persistently on the issue of health care, but their exchanges proved inconclusive. Where he may have left Bradley vulnerable was over the future of Medicare. Challenged by Gore to explain why he has not set aside money to preserve Medicare, Bradley noted that the system should remain solvent until 2017 and that the more pressing problem facing the country is the growing ranks of the uninsured. But few programs are more important to Democratic voters, and Gore is likely to press that point further in the coming weeks.

Stylistically the debate reinforced the images that the two men have projected on the campaign trail for months. Gore offered programmatic laundry lists and his answers often ranged far from the questions posed. Bradley too was freewheeling in his answers, but veered toward the philosophical rather than the programmatic when he had the opportunity.

Bradley and Gore meet again on Sunday morning for another debate, this time on NBC's "Meet The Press." But tonight's encounter may have signaled where this Democratic race is heading in the coming weeks. Both candidates have set their strategies, found their voters and know what they want to say. The voters may not find big differences on policy to choose from but they will be able to choose from two strikingly different candidates to lead their party.