In June 2020, when lawyers for Mississippi asked the Supreme Court to hear a case involving the state’s 15-week abortion ban, they took care to assure the justices that this wasn’t the big one, the case that would call on the court to overrule Roe v. Wade, the 1973 decision establishing a constitutional right to abortion.

“To be clear, the questions presented in this petition do not require the Court to overturn Roe or Casey,” their petition for review said, referring to the 1992 decision in which a closely divided court declined to do away with Roe.

The only reference to such a dramatic step came in an obliquely worded footnote: “If the court determines that it cannot reconcile Roe and Casey with other precedents or scientific advancements showing a compelling state interest in fetal life far earlier in pregnancy than those cases contemplate, the Court should not retain erroneous precedent.”

The justices let Mississippi’s request languish for nearly a year before agreeing to hear the case — limited, the court said, to a single question: “Whether all pre-viability prohibitions on elective abortions are unconstitutional.”

But when Mississippi filed its full brief with the court this summer, the gloves came off — not coincidentally, perhaps, because in the intervening months, Justice Ruth Bader Ginsburg had died and been replaced by Justice Amy Coney Barrett, an avowed critic of the court’s abortion jurisprudence.

Roe and Casey are egregiously wrong,” the state argued. “Overruling Roe and Casey makes resolution of this case straightforward.” From a mere footnote, the case for overruling Roe mushroomed into the vast majority of the brief.

The justices, who this week set Dec. 1 for oral argument in the case, get to decide what they will decide, so it’s possible they’ll be put off by Mississippi’s bait-and-switch and avoid tackling that question. That’s what the Biden administration urged in the brief it filed last week, in the case Dobbs v. Jackson Women’s Health Organization.

Mississippi has “now dramatically changed course, devoting their merits brief to a frontal assault on Roe and the fifty years of precedent reaffirming its central holding. The Court has previously declined to indulge such tactics,” it argued. “It may wish to do the same here — particularly given the gravity of the issue petitioners have belatedly injected into this case. But if the Court considers that issue, it should once again reaffirm Roe’s central holding that the Constitution protects a woman’s right to terminate her pregnancy before viability.”

Will the court hold back? Maybe. It’s clear that none of the six conservative justices believes that the Constitution protects a right to abortion, but that’s different from saying a majority is willing to say flatly that Roe is overruled.

One sign: In 2020, Chief Justice John G. Roberts Jr. voted with the court’s liberals (who then numbered four) to invalidate a Louisiana abortion law that was effectively identical to a Texas law the court had struck down four years earlier — over Roberts’s dissent. That suggests the chief justice, at least, is not eager to take the plunge.

But Roberts’s relevance has been diminished; he now has five conservative colleagues, who may not share his reticence. And an ominous sign in the opposite direction: The court chose to review the Mississippi case despite the fact that it satisfied none of the usual criteria for review — no circuit splits, conflict with precedent or unsettled question of law.

My best guess is that the court won’t accept Mississippi’s invitation — but also that supporters of abortion rights shouldn’t take too much solace in this facade of restraint. The constitutional right to abortion hangs by a fraying thread. The question the justices have already agreed to decide may sound less threatening than overruling Roe — in practice, it threatens to amount to the same thing.

The many abortion cases that have come to the court since 1973 have involved restrictions on abortion — rules such as mandatory sonograms and waiting periods, or bans on certain abortion methods; the test was always whether those restrictions impose an “undue burden” on abortion access. But the court has never approved a flat prohibition on abortion before the fetus is viable, about 24 weeks into pregnancy.

If Mississippi’s prohibition on abortion after 15 weeks is allowed to stand, what stops a state from outlawing abortion at 12 weeks, or 10, or — as Mississippi has already tried to do — six? This would, the Biden administration points out, “invite perpetual give-it-a-try legislation.”

As the abortion clinic challenging the law asks in its brief, “Stripped of the viability line, how would federal courts evaluate these arguments on a case-by-case basis? What state interests would count as compelling or otherwise sufficiently strong to categorically outweigh the individual liberty interest at stake?”

This slope isn’t just slippery; it would be perilous — for women, certainly, but also for the courts as they try to stake out a toehold on this treacherous terrain. There is not much hope, given the makeup of this court, of invalidating the Mississippi law. The looming choice is between two forms of disaster, immediate and slow-motion.