After two decades of battling over the constitutional right to abortion, the two warring camps have finally found something on which they can agree: The abortion-rights side is about to lose.

And abortion-rights advocates, looking ahead to the November elections, have essentially decided that if they are going to lose, they may as well lose big. In a go-for-broke legal strategy, they have set what they acknowledge to be an unrealistic goal -- a ringing reaffirmation of Roe v. Wade, the 1973 ruling establishing abortion as a constitutional right.

"The litigation strategy is: If indeed we don't have Roe, American women ought to know about it and the court shouldn't be duplicitous," said Judith L. Lichtman, president of the Women's Legal Defense Fund Inc. "I don't think we have anything to lose."

This morning, the Supreme Court hears oral arguments in a challenge to Pennsylvania's abortion law, the court's 18th abortion case -- and the third from Pennsylvania -- since 1973. A ruling in the case, Planned Parenthood of Southeastern Pennsylvania v. Casey, is expected by July.

With only two firm advocates of abortion rights remaining on the high court -- Justices Harry A. Blackmun and John Paul Stevens -- abortion-rights groups concede that they have little hope of mustering a majority to strike down the law, even though nearly identical provisions have previously been ruled unconstitutional.

The law requires married women to notify their husbands that they plan to have an abortion, imposes a 24-hour waiting period on women seeking abortions, and mandates that doctors and counselors provide detailed information about fetal development and alternatives to abortion.

What both sides in the Pennsylvania case will be watching for is not so much the bottom line of the court's eventual ruling, but how it gets there.

Few believe that there are five votes on the court to reaffirm the core holding of Roe: that abortion is one of the limited category of fundamental rights that are entitled to the highest degree of constitutional protection (other such rights include the right to travel, to marry and to procreate) and that a woman's right to choose abortion, in the early stages of pregnancy, is nearly absolute.

On the other hand, with the notably fervent exception of Justice Antonin Scalia, the court has shown no inclination to announce explicitly that Roe is overruled.

Between ringing reaffirmation and explicit repudiation lie two main alternatives for the court.

One is the "undue burden" test suggested by Justice Sandra Day O'Connor but not endorsed by any other justice. Under that test, the court would ask whether a restriction on abortion places an "undue burden" on women -- defined as an "absolute obstacle" or "severe limitation" on the abortion decision.

The 3rd U.S. Circuit Court of Appeals in Philadelphia, assessing the Pennsylvania statute, employed the undue burden test. It upheld most of the law but, splitting 2 to 1, struck down the husband notification provision.

The second alternative is the "rational basis" test. Under that test, abortion would be stripped of special constitutional protection and abortion restrictions would be treated like any other statute -- a law regulating drivers' licenses, for example. In assessing an abortion law, the court would simply inquire whether the regulation is "reasonably designed to serve a legitimate state interest."

Abortion-rights advocates have announced that neither alternative will do; both, they say, are tantamount to overruling Roe without saying so.

"Roe has always said that the right to choose abortion is a fundamental right," said Kathryn Kolbert, the American Civil Liberites Union lawyer who will argue the case. "Regulations that burden that right as well as total bans have been outlawed, and anything short of that standard is really just an empty gesture to the women of this nation."

In friend-of-the-court briefs, the abortion-rights side attempts to drive that point home. A brief on behalf of 30 senators and 118 representatives emphasizes the importance of stare decisis, the principle that the court should not lightly discard its precedents. A coalition of 178 organizations offers alternative bases for finding constitutional protection for abortion rights. A brief on behalf of 250 historians outlines the historical basis for finding a right to abortion.

Some of the abortion-rights briefs adopt a real-life perspective. For example, the Pennsylvania Coalition Against Domestic Violence talks about the threat the spousal notice requirement -- even with its exception for women who fear physical harm if they tell their husbands -- poses to battered women.

The NAACP Legal Defense and Educational Fund and others concentrate on the economic hardship of a 24-hour waiting period, with its requirement of two trips to a clinic potentially over a long distance, may pose to poor women.

The American Psychological Association argues that the "informed consent" provisions, which require that women be given a brochure describing "the possible detrimental psychological effects of abortion," has no support in the psychological literature and "may result in unnecessary anxiety, stress and harm to many women."

"I used to believe that the powers of good persuasive argument made a difference," Kolbert said wryly. "I'm not willing to give that up totally."

On the other side, the State of Pennsylvania contends that the court can uphold the law without overturning Roe. It endorses the undue burden test but says the appeals court was wrong in finding that the husband notification provison constituted an undue burden.

Some antiabortion advocates, including the Bush administration, are pressing the court to go further and either explicitly overturn Roe or adopt a rational basis test.

For example, said James Bopp, general counsel of the National Right to Life committee, "The brief that we did was addressed to those justices who might be considering the undue burden test. . . . Obviously, O'Connor has an interest in that, and we don't know to what degree others may, and so we felt it was necessary to point out the problems with that test."

The difference between those two approaches may be more cosmetic than real. Pennsylvania Attorney General Ernest D. Preate Jr. said in an interview that even an outright ban on abortion, with an exception for life-endangering pregnancies, could be upheld under an undue burden test.

That, said Preate, is because even an undue burden may be allowed if it is justified by what the court calls a "compelling state interest" -- and the state has a compelling interest in protecting potential human life throughout pregnancy, he said. (Under Roe, that interest becomes compelling only at the point of viability for the fetus, approximately the third trimester.)

Friend-of-the-court briefs on the antiabortion side in part also go head to head against the points made by the abortion-rights advocates. For example, competing groups of members of Congress argue the limited force of stare decisis and the erosion that has already undermined Roe's legal status; the American Association of Pro-Life Obstetricians and Gynecologists takes on the American Colleges of Obstetricians and Gynecologists.

There is no guarantee that a majority of the court will coalesce around any particular standard, although at least four justices -- Chief Justice William H. Rehnquist and Justice Byron R. White, the two original dissenters in Roe, joined by Scalia and Justice Anthony M. Kennedy -- appear ready to adopt a rational basis test.

To forge a majority, they would need to secure the vote of either Justices David H. Souter or Clarence Thomas, who have not yet voted on an abortion case.

There is also no guarantee that the court will straightforwardly announce what test it is adopting. In recent abortion cases, the court has seemed almost deliberately obscure in its wording and analysis.

On the other hand, the justices know that if they somehow manages to duck a clear answer to the constitutional status of abortion on this round, the issue will be back before them soon.

Just last week, the federal appeals court in California struck down a Guam law that made abortion a crime in almost all circumstances, guaranteeing that the abortion issue will be back again next term if it is not settled this year.

OPPOSE ROE V. WADE

CHIEF JUSTICE WILLIAM H. REHNQUIST

One of two original dissenters in Roe v. Wade, he believes there should be no special constitutional protection for abortion.

JUSTICE BYRON R. WHITE

The other dissenter in the 1973 Roe ruling, in which he accused the majority of engaging in "an exercise of raw judicial power."

JUSTICE ANTHONY M. KENNEDY

He joined Rehnquist and White in the 1989 Webster v. Reproductive Health Services ruling in which they endorsed a "rational basis" standard of review for abortion regulations.

JUSTICE ANTONIN SCALIA

A staunch opponent of abortion rights, he has scolded the court for failing to announce explicitly that it is overruling Roe and get itself out of the business of deciding abortion cases.

SUPPORT ROE V. WADE

JUSTICE HARRY A. BLACKMUN

Author of the Roe ruling, in which he found that the constitutional "right of privacy...is broad enough to encompass a woman's decision whether or not to terminate her pregnancy." He said last year that "the votes are there" to overrule Roe.

JUSTICE JOHN PAUL STEVENS

He has been a staunch supporter of abortion rights since joining the court in 1975, most recently writing the 1990 ruling in Hodgson v. Minnesota that struck down a law that required a minor to notify both parents before obtaining an abortion and did not provide the alternative of going before a judge.

VIEWS ARE A QUESTION MARK

JUSTICE SANDRA DAY O'CONNOR

She has criticized the trimester framework set out in Roe but has shied away from saying outright that it should be overruled. Instead, she has suggested that abortion regulations be tested to see whether they impose an "undue burden" on women.

JUSTICE DAVID H. SOUTER

He has never ruled directly on an abortion case, although he voted last year to uphold regulations that prohibited federally funded family planning clinics from providing women with information about abortion. He has been in the middle of the conservative court and so might take a position similar to that of Justice O'Connor.

JUSTICE CLARENCE THOMAS

The newest justice, he has never ruled on an abortion case and told the Senate Judiciary Committee that he had never debated the merits of Roe v. Wade. However, based on his praise for an anti-abortion article and his conservative performance since joining the court, he is expected to be hostile to abortion rights.