The controversy over a botched television commercial by a leading abortion rights group attacking Supreme Court nominee Judge John G. Roberts Jr. once again demonstrated the power of abortion to inflame the political debate -- while illuminating the often difficult relationships between political parties and their most passionate activists.

For the moment, it is Democrats who are facing most acutely the challenge of satisfying an important constituency without offending the political center. NARAL Pro-Choice America's decision Thursday to take off the air an ad that had been roundly denounced as misleading vividly underscored the dilemma.

Abortion rights groups and their allies, who are providing money and energy in the campaign to defeat the nomination, want to use the Roberts nomination to raise alarms about the future of legal abortion. While opposed to Roberts, they also hope to boost public consciousness on the issue at a time when they have seen erosion in activism, particularly among younger women who female strategists say are less committed to the fight than their mothers' generation.

But even if Roberts were an easier target -- which Democrats concede privately he is not -- the Supreme Court battle comes at a moment when some Democrats have sought to soft-pedal their rhetoric on abortion. They are looking for ways to appeal to more conservative voters in rural and other areas who might be attracted to Democrats on economic issues, but feel unable to cross what they see as a yawning divide on cultural issues.

In a private meeting late last year with some of his party's leading organizers and strategists, Sen. John F. Kerry (D-Mass.) pointedly blamed abortion and gay rights for his loss to President Bush in last year's election -- stunning and angering his audience. But Kerry also has said repeatedly that he would not support someone for the Supreme Court who would vote to overturn the 1973 Roe v. Wade decision creating a legal right to abortion. All by himself, Kerry seemed to encompass the party's conflicting sentiments about the issue.

Other Democrats have suggested the party needs a new strategy for talking about abortion. Sen. Hillary Rodham Clinton (N.Y.), Sen. Edward M. Kennedy (Mass.) and Democratic National Committee Chairman Howard Dean have all signaled this year that Democrats have cast the abortion debate too strongly in terms of legal rights and have not spoken enough about the moral issues and responsibilities that also infuse the topic.

Talk of a new approach to abortion by Democratic officials has frustrated activists, who see it as a retreat on an issue that has been central to the party's core coalition. "When you say this to Democratic leaders, they deny this is happening," said Eleanor Smeal, president of the Feminist Majority Foundation. "So in a way we feel like we're fighting a mirage."

Some Democrats fear that the NARAL ad controversy, because it has damaged the group's credibility on the eve of the hearings, could make it more difficult for Democratic senators to question Roberts closely on abortion and the right to privacy and still avoid appearing to be captives of their own constituencies. But they also risk offending their own base if they are not aggressive.

For the past three decades, no issue -- with the possible exception of race -- has more consistently roiled American politics. Public opinion on abortion has been remarkably stable over that period, with majorities favoring both abortion rights and some restrictions on the availability of the procedure. But the political potency of the issue has ebbed and flowed in reaction to events, often those dictated by the high court.

Currently the status quo favors Republicans, according to analysts in both parties, with the debate now focused on the enactment of restrictions that often have broad support in public opinion surveys, rather than on abortion's basic legality. But many of those same analysts agree that any prospect of a reversal of Roe v. Wade or of significantly greater intrusion by the courts into the deeply personal moral issues could dramatically change the equation to the benefit of the Democrats.

"There's a lot of centrism among the public about abortion," said Andrew Kohut of the Pew Research Center for the People and the Press. "It's very easy for the activists to scare most Americans, who have a nuanced view of abortion, either from the pro-life or the pro-choice perspective."

Passion has long defined activists on both sides of the abortion wars, but they are true believers in a sea of conflicted Americans. "Public opinion has been remarkably stable for 30 years and at one and the same time deeply contradictory," said Karlyn Bowman of the American Enterprise Institute.

The Los Angeles Times in a poll taken in June 2000 asked people whether they agreed or disagreed with the statement "Abortion is murder." In that poll, 56 percent of respondents said they agreed. On the other hand, majorities say the choice of having an abortion should be left to a woman and her doctor. A poll taken in May by NBC News and the Wall Street Journal found 55 percent of those surveyed agreed with that view.

Government intrusion in these kinds of moral questions makes many people uncomfortable, as demonstrated by the reaction to Congress's intervention in the case of life-support patient Terri Schiavo this spring.

Republicans know that, given Roberts's thin judicial record, polite demeanor and blue-chip legal credentials, the nominee has offered Democrats little to attack. As a result, his supporters on the right have adopted a low-key strategy that mirrors the incremental approach they have pursued in recent years to restrict the availability of abortions.

"The pro-choice community has to try very hard to make him look like he's already made a decision on this issue, whereas the more conservative or pro-life side wants to try to minimize this issue," said Debbie Walsh, director of the Center for American Women and Politics at Rutgers University.

Activists on the right have long advocated overturning Roe v. Wade, but few Republican politicians want to make that the rallying cry of this or any Supreme Court battle in the near future. Tony Perkins of the Family Research Council said that, even with Roberts on the court, there would not be a majority in favor of reversing Roe. But he noted that, on issues such as parental notification and late-term abortion, Roberts's "presence on the court could make a difference."

But before Roberts was nominated, other conservative spokesmen talked openly about the importance of the abortion issue in Supreme Court vacancies. "Let's be honest about it, shall we?" Paul M. Weyrich said as he discussed the Supreme Court vacancy on his Internet radio show even before Roberts was picked. "What this issue has been about from day one is right to life. The abortion issue is the critical issue here."

David O'Brien, a professor at the University of Virginia who has studied the area, predicts a gradual cooling of the debate because of access to newer forms of contraception. Others, however, predict that any perceived threat to Roe will mobilize swing voters who otherwise pay only limited attention to the issue, as happened in 1989 after the court ruled in Webster v. Reproductive Health Services that states were free to restrict abortions.

In the past decade, public perceptions of a woman's right to have an abortion vs. the rights of a fetus have shifted in the direction of the fetus, due in part to advancing technology -- for example, the use of sonograms to capture vivid images of the developing fetus. But Democratic pollster Geoffrey Garin said once questions of a woman's health come into the equation, the public believes the government should stay out of the decision-making. "The Roberts hearings provide the forum to move this conversation back in that direction," he said.

Roberts's views on the issue are largely unknown or ambiguous, but both sides know that because he would replace Justice Sandra Day O'Connor, who was the swing vote on many abortion cases, he could have an enormous influence on the politics of abortion in the future.