With states racing to pass ever more restrictive abortion laws and a polarized nation fixated on what the justices may do about them, their first step was one of compromise and caution.

The high court on Tuesday upheld one part of a restrictive Indiana law that had been struck down by lower courts, but it decided against reviving a more controversial portion of the law that would have limited a woman’s opportunity to get an abortion.

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More opportunities to limit — or eliminate — the fundamental right established by Roe are coming to the court. How the justices respond will define the court in the public’s mind.

A look back at what happened exactly 27 years ago next week provides a moment of pause for both sides of the abortion fight, as well as for President Trump, who made the campaign pledge that overturning Roe “will happen automatically in my opinion because I am putting pro-life justices on the court.”

On June 3, 1992, three Republican-nominated justices who once were thought to hold similar promise — Sandra Day O’Connor, Anthony M. Kennedy and David Souter — circulated a ruling that reaffirmed what they called the “essential holding” of Roe. Their decision recognized “the right of the woman to choose to have an abortion before viability and to obtain it without undue interference from the state.”

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If 1973’s Roe has the name recognition, 1992’s Planned Parenthood of Southeastern Pennsylvania v. Casey sets the “undue burden” standard by which restrictive abortion laws sprouting around the nation — including the Indiana law at stake this week — are judged.

In Casey, even justices who had been sharply critical of Roe were not ready to take the final step to overrule it. As retired Justice John Paul Stevens explains in his new memoir, “The Making of a Justice,” the vote count in the Supreme Court’s private conference after oral argument in the case revealed the necessary five votes to overrule Roe.

“Harry and I both assumed that the result would be explained in an opinion overruling Roe v. Wade, and Chief Justice [William H.] Rehnquist circulated a draft opinion for the court on May 27, 1992, that met our expectation,” writes Stevens, referring to Justice Harry A. Blackmun, who had written Roe nearly 20 years before.

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What the rest of the court did not know was that Kennedy had changed his mind. He, O’Connor and Souter were working behind the scenes to devise a compromise that upheld Roe’s core but made it easier for states to enact restrictions on the procedure.

“Sandra, David and Tony surprised us,” Stevens remembered in an interview with The Post earlier this month.

Stevens and Blackmun thought all of the challenged provisions of the Pennsylvania law should be struck down. But once the trio circulated a draft of their opinion, Stevens moved quickly to embrace the parts with which he and Blackmun could agree.

He suggested a structural change: Confine criticism of past cases to the end of the opinion, so he and Blackmun could join the first part.

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An opinion that speaks for the court “for 25 pages would be far more powerful than one that starts out as a plurality,” Stevens writes in the memoir. “They adopted most of my suggestions.”

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The decision was a shock. Kathryn Kolbert, who argued the case for challengers of the restrictive Pennsylvania law, said recently it took her several hours to realize she should consider the ruling a victory. It upheld three of the four contested provisions, including a 24-hour waiting period and a requirement that minors have the consent of a parent or judge, and struck only the one requiring a woman to notify her husband before receiving an abortion.

But it vindicated Kolbert’s approach to the case, which was to pressure the justices to state unequivocally whether Roe remained the law of the land.

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“Our strategy was based on the assumption that there were five votes on the court to overturn Roe, and we were right,” Kolbert said in an interview. Rehnquist’s draft opinion said that “the Court was mistaken in Roe when it classified a woman’s decision to terminate her pregnancy as a ‘fundamental right.’ ”

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If the answer on Roe was to be no, Kolbert said, abortion rights supporters wanted a clear message they could use to galvanize voters. “We wanted the public to understand what was at stake and get it settled before the 1992 presidential election.”

It was unclear at the time what had transpired after the case was argued. But the story has emerged since, from Blackmun’s papers and from books that have detailed the justices’ tense negotiations.

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O’Connor and Souter persuaded Kennedy to change his mind about overturning Roe, convincing him that the court’s reputation would suffer if it toppled the landmark ruling. Their opinion said that Roe could be overturned only “at the cost of both profound and unnecessary damage to the court’s legitimacy.”

O’Connor, known for pragmatism and unadorned prose, was willing to indulge Kennedy’s tendency for the lofty flourish, author Evan Thomas writes in his new biography of O’Connor, “First.”

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Thus, the opinion opened: “Liberty finds no refuge in a jurisprudence of doubt.” It contains rhetoric mocked by conservatives who were stung by Kennedy’s change of heart.

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“At the heart of liberty is the right to define one’s own concept of existence, of meaning, of the universe, and of the mystery of human life,” Kennedy wrote.

O’Connor did not quibble, Thomas wrote,: “She understood that it took some courage for the Catholic Kennedy to countenance any compromise or middle way on abortion rights.”

In the months from argument to decision, the court’s conservatives grew worried about Kennedy. In her book “Supreme Conflict,” longtime Supreme Court correspondent Jan Crawford wrote that Justice Antonin Scalia, who desperately wanted Roe overturned and the issue of abortion returned to the states, sensed trouble with his fellow Reagan nominee.

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He called Kennedy and asked him to take an after-dinner walk around the neighborhood in McLean, Va., where the two justices owned homes.

“By the end of the walk, Scalia felt confident Kennedy was a solid vote,” Crawford wrote. “He went home thinking the five would stand together.” Kennedy did not say a word to Scalia about the compromise opinion he was writing with O’Connor and Souter, she reported.

Scalia’s disgust was evident in his dissent: “The Imperial Judiciary lives.”

And it has been up to judges since to decide what constitutes an undue burden.

The U.S. Court of Appeals for the 7th Circuit saw it in Indiana’s list of impermissible reasons — race, gender or disability of the fetus — for getting an abortion.

“These provisions are far greater than a substantial obstacle; they are absolute prohibitions on abortions prior to viability, which the Supreme Court has clearly held cannot be imposed by the state,” wrote Judge William J. Bauer.

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Judge Daniel A. Manion agreed, but did not like it. “That today’s outcome is compelled begs for the Supreme Court to reconsider Roe and Casey,” he wrote.

The sentiment was endorsed Tuesday by Justice Clarence Thomas, a dissenter in Casey and the only remaining justice from the court that decided that case.

Thomas, who has previously urged the court to overturn Roe, wrote a 20-page statement. In it, he likened decisions to abort a fetus because of a diagnosis of Down syndrome or other disability, or because of race or sex, to “modern-day eugenics.”

“Whatever else might be said about Casey,” Thomas wrote, “it did not decide whether the Constitution requires States to allow eugenic abortions.”

He added: “Having created the constitutional right to an abortion, this Court is dutybound to address its scope.”

It will have many opportunities.

The recently passed Alabama law virtually forbids abortion except in cases where the woman’s life is at stake or because of a severe fetal abnormality. It cannot be squared with Casey or Roe.

It joins other restrictive abortion laws passed in a flurry of action from conservative states. As in 1992, they are aimed at a Supreme Court with justices known to be supportive of abortion restrictions and reinforced by new members nominated by a Republican president who has promised to overturn Roe. A presidential election looms.

“Yes, it sounds like deja vu all over again,” Kolbert said. But she makes a pessimistic prediction for her side about a Casey-like compromise.

“It won’t happen again,” she said.

The reason? “Justice Roberts is not Justice Kennedy,” she said.

On the one hand, Chief Justice John G. Roberts Jr. is seen as the best hope for abortion rights proponents. He prefers to move the court’s jurisprudence incrementally rather than with dramatic gestures, as overturning Roe would be. He earlier this year voted with liberal members of the court to keep a restrictive Louisiana law from going into effect until the Supreme Court could decide whether to review it.

But unlike Kennedy, Roberts is a product of the conservative Republican movement in Washington. As chief justice, Kolbert notes, he has never found that a government restriction on abortion amounted to an “undue burden” on the woman seeking it.

The court’s other conservatives are even less unlikely to provide a surprise. Presidents of both parties have become far more focused on the backgrounds of their Supreme Court nominees since the time Republican presidents took chances on Souter, Kennedy and even O’Connor. “No more Souters” became a catchphrase for the conservative legal movement.

Trump’s choices for the court — Neil M. Gorsuch and Brett M. Kavanaugh — have few votes on the issue in their pasts as lower court judges but were strongly supported by antiabortion activists.