WHEN Roe vs. Wade came down in 1973, holding that women had a fundamental right of access to abortion, its opponents launched two offensives that persist to this day.
The first was to appoint to the Supreme Court conservative justices who would overrule Roe, leaving the controversy to the winds of politics rather than law. The second was to enact legislation cutting back on abortion rights as much as possible.
Roe opponents have won some skirmishes, but so far they are still losing the war. For the anti-abortion movement, Monday's Supreme Court decision in the Pennsylvania abortion case was a rout.
In Planned Parenthood vs. Casey, the court upheld some but not all provisions of a law designed to make obtaining an abortion more time-consuming and expensive but not to prevent or prohibit it.
The court upheld a law requiring doctors to give a woman seeking an abortion a litany of facts about her fetus and about the alternatives to abortion -- a warning about the consequences of exercising her rights.
It also upheld a requirement that a woman wait 24 hours after hearing this information before going ahead with an abortion, a requirement that a detailed record of the abortion be kept and a requirement that when a minor seeks an abortion, her parents or a court be notified.
But the court drew the line at a requirement that a married woman certify to her doctor that she has told her husband she is seeking an abortion. It held that, in the late 20th century, husbands are not their wives' keepers and may not be given veto power over pregnancies.
True, this holding cuts back on some post-Roe decisions, giving the states greater leeway than they have had in recent years to impose added delay, cost, discomfort and inconvenience on a woman's effort to obtain an abortion.
But, crucially, the court ringingly reaffirmed the core of Roe. It reaffirmed that the ultimate decision-making authority about whether to continue or end a pregnancy must rest with a pregnant woman, at least throughout the greater part of the pregnancy before the fetus is "viable" -- capable of living outside the womb.
The court deemed this decision a matter of protected constitutional liberty -- the freedom to make our most personal and intimate choices for ourselves rather than have them dictated to us by the state.
If Roe was thus reaffirmed, how did the court manage to uphold so much of Pennsylvania's law?
It split the world of abortion regulation in two. After Monday's decision, abortion still may not be made a crime. No woman seeking an abortion may be sent to jail or relegated to butchery in back-alley botch jobs.
Nor may a state place any other "undue burden" or "substantial obstacle" in the path of a woman seeking an abortion.
But if criminal penalties and husbands' vetoes are out, states are now free to impose some hassles and headaches on women seeking abortions. Future cases will turn on the degree of burden imposed -- has the state made abortion nearly impossible or merely less convenient?
But the decision ties the hands of any state that might otherwise have tried to eliminate abortion altogether.
At least for now. At least as long as Justice Harry A. Blackmun, 83, remains on the court.
For the reaffirmation of Roe, it is crucial to note, was decided by a vote of only 5-4. Justice Blackmun, author of the landmark Roe decision, has endured hate mail and buckshot for his efforts.
Term after term during nearly 12 years of the Reagan and Bush administrations, he has waited to see whether new appointments to five vacancies would undo his handiwork.
Writing separately, Justice Blackmun praised the "act of personal courage and constitutional principle" embodied in the joint opinion of Sandra Day O'Connor, Anthony Kennedy and David Souter, which was crucial, along with his and Justice John Paul Stevens' votes, to the outcome.
But in an extraordinary personal afterword, Justice Blackmun noted: "I am 83 years old. I cannot remain on this court forever, and when I step down, the confirmation process for my successor may well focus on the issue before us today."
In other words, Roe and its vision of personal liberty is but one vote away from the overruling its opponents have long sought.
The four dissenters (who agreed with its result insofar as it upheld the Pennsylvania restrictions) were Chief Justice William H. Rehnquist and Justice Byron White, the original dissenters in Roe, as well as Justice Antonin Scalia and the newest justice, Clarence Thomas.
These four justices would overrule Roe root and branch and remit abortion regulation entirely to the political process, accepting as constitutional whatever patchwork of results might follow. And they would need only one vote to do it.
But the very fragility of the ruling is what makes it doubly a rout for the anti-abortion movement. It is a rout to the extent that Roe was narrowly reaffirmed. But it is also a rout to the extent that Roe hangs by a thread or a heartbeat. For the last three years have witnessed an extraordinary turnabout in abortion politics.
Roe spawned an extraordinarily well-organized and unflappable anti-abortion political movement. It was flatly defeated in its efforts to overturn Roe by declaring a fetus a form of human life. But, undaunted, it succeeded at chipping away at what it could not topple.
The anti-abortion movement has succeeded in limiting abortions for poor women and for teen-agers.
It has succeeded in withdrawing federal funding from the performance of abortions and ultimately even from abortion counseling and referral. And pregnant teen-agers are hampered in ways not permissible for adults.
But in 1989, when the court's decision in Webster vs. Reproductive Health Services came down, the tables suddenly turned.
The pro-choice movement read the decision, which closed public hospitals to abortion even where a woman paid the full cost, threatening abortion rights even for affluent adults. And the long-slumbering giant of pro-choice politics was awakened to life.
Since 1989, money has poured into the coffers of the pro-choice movement. And anti-choice positions have proved fatal to politicians of both parties at the polls. In the volatile politics of an election year dubbed the "Year of the Woman," such a fate may often be repeated.
The House Judiciary Committee is considering the "Freedom of Choice Act," which would codify through legislation the protections in Roe that a future court might rescind as a matter of constitutional principle. If it passes, a veto by President Bush will put him and other Republicans in an awkward position before an electorate that overwhelmingly supports some personal choice about abortion, at least in a great many cases.
It might seem to some, then, that Roe, even if right, is no longer needed. If a pro-choice majority commands the polls, who needs a pro-choice court majority?
To take this view would be a grave mistake. Constitutional protection exists precisely for what is too precious and fragile to be left to politics. Whatever the polls might say, a woman's right to control her reproductive life is such a matter.
So abortion is not the only constitutional issue in politics this year. As Justice Blackmun has pointedly reminded us, so is the Supreme Court.
Kathleen M. Sullivan is professor at Harvard Law School.