Mississippi is asking the Supreme Court on Wednesday to affirm its legislature’s judgment that it should be practically impossible to obtain an abortion in the state after 15 weeks of pregnancy.

But the state’s goals are more ambitious than that, significantly raising the stakes on the most important challenge to abortion rights in decades.

Mississippi also has a six-week ban on abortions that has been put on hold by lower courts. And if the Supreme Court agrees with the state’s assertion that Roe v. Wade should be overturned, the state already has decided to ban the procedure altogether, except in cases of rape or “preservation of the mother’s life.”

It is not alone.

“If the court does overrule Roe and says that bans on abortion before viability are fair game, there are about half of the states in the country that would be poised to either ban abortion entirely or at an extremely early point in pregnancy,” said Julie Rikelman, an attorney for the Center for Reproductive Rights, which represents Mississippi’s only abortion clinic.

White House press secretary Jen Psaki told reporters Tuesday that President Biden is “deeply committed to the constitutional right established in Roe” and believes the Mississippi law “blatantly violates the constitutional right to safe, legal abortions.”

Mississippi initially told the Supreme Court it could square its 15-week ban with Roe, decided in 1973, and the court’s 1992 decision in Planned Parenthood v. Casey, which reaffirmed the constitutional right.

Casey said that while states have an interest in regulating abortion, they cannot implement bans before viability or erect other restrictions that unduly burden the right.

But after the court accepted Mississippi’s case, the state decided to shoot for the moon. It said both Roe and Casey should be overturned.

“Nothing in constitutional text, structure, history, or tradition supports a right to abortion,” the state told the court. States should be free to ban elective abortions as long as they show the prohibition promotes a legitimate government interest, it said.

The revamped strategy was fashioned for a transformed Supreme Court. The court now has six conservatives, three of them nominated by President Donald Trump, who said that his choices would reject Roe.

It is unclear whether Justices Neil M. Gorsuch, Brett M. Kavanaugh and Amy Coney Barrett are on board with such a move, which would dismantle nearly a half-century of abortion jurisprudence.

But the court has never even thought worthy of review a state law that banned abortion before viability. And all three of the Trump nominees were in the court’s slim majority that allowed an unusual Texas law to go into effect, virtually eliminating abortion after six weeks of pregnancy in the nation’s second-largest state.

“This is the most worried I’ve ever been,” Shannon Brewer, director of Mississippi’s only abortion clinic, the Jackson Women’s Health Organization, told reporters in a briefing.

Even the most conservative appeals courts have struck down bans similar to Mississippi’s because of the Supreme Court’s unambiguous guidelines in Roe and Casey.

As Judge Patrick E. Higginbotham wrote for a panel of the U.S. Court of Appeals for the 5th Circuit in stopping Mississippi’s law: “In an unbroken line dating to Roe v. Wade, the Supreme Court’s abortion cases have established (and affirmed, and reaffirmed) a woman’s right to choose an abortion before viability.”

When the Supreme Court said it would review that decision, it said it was limiting its inquiry to “whether all pre-viability prohibitions on elective abortions are unconstitutional.”

The outcome, according to Sherry Colb, a Cornell University law professor who has written extensively about abortion rights, “is not a nail-biter.”

“The Supreme Court will uphold the Mississippi 15-week ban,” she said. “It will say that it is not overruling Casey because it does not need to reach the question, since a 15-week ban does not impose an undue burden. That statement will be at best manipulative and at worst dishonest.”

Commentators on the left and right agree that it is difficult, if not impossible, to uphold the law without altering the court’s clear instruction that pre-viability bans are unconstitutional. Viability is usually defined as between 22 and 24 weeks of pregnancy, months later than Mississippi’s ban.

“It’s very hard for me to see how the court could uphold the 15-week law without entirely eliminating the constitutional entitlement to elective abortions in Roe and Casey,” said University of Notre Dame law professor Sherif Girgis, a former clerk to Justice Samuel A. Alito Jr. “And by that, I don’t mean that I think that a middle ground would be unsound. . . . I actually mean it would be impossible to imagine a lawyerly argument” that could embrace both.

Edwin Meese III, President Ronald Reagan’s attorney general from 1985 to 1988, said anything less than overturning Roe and Casey should be considered a loss for the right.

“It is not simply the future of abortion that is at stake in Dobbs v. Jackson Women’s Health,” he wrote in a Washington Post opinion piece. “The court’s answer will also determine whether the dominant conservative legal project of the past 40 years, to restore neutral principles to constitutional interpretation, has been a success.”

While legal experts may debate whether Roe’s finding of a fundamental right to abortion has a constitutional basis, polls show public support for Roe has remained steady over the years.

Chief Justice John G. Roberts Jr. has shown an inclination for incremental change in law that does not prompt banner headlines. And last term, Kavanaugh and Barrett declined to join a move by fellow conservatives to overturn a court precedent on religious rights that has long been a target of the right.

Barrett wrote that she thought the previous case might have been wrongly decided but that it was not clear what should replace it.

At a panel discussion on the Mississippi case sponsored by the Federalist Society, University of Virginia law professor Richard Re said the court has not really prepared the public for an outcome that would overturn decades of abortion rights.

That might suggest some sort of half-measure, as the court has employed before. That would set off rounds of legal battles, such as over Mississippi’s six-week ban.

It would “intensify what is already a pretty vigorous process of . . . testing the waters to see how far the court will go and how quickly in undermining Roe,” said Mary Ziegler, an abortion law expert at Florida State University. “But I would almost expect that that would be a plus for some of the justices on the court, especially those with institutionalist concerns.”