Thirty years ago, the Supreme Court nearly struck down Roe v. Wade in a Pennsylvania case. The justices chose another way.

It was months before a pivotal national election. A strong conservative majority had been cemented on the U.S. Supreme Court, and legislators in one state had passed a law restricting abortion access that they hoped, through the court challenges that followed, would become the vehicle for overturning Roe v. Wade.

In a legal opinion on that measure issued months before the Supreme Court would officially rule, Samuel A. Alito Jr. fiercely defended the notion that states had a legitimate interest in imposing restrictions on when and under what circumstances abortions could be provided.

The year was 1992. The case? Planned Parenthood v. Casey, one that originated in Pennsylvania.

The political atmosphere surrounding that landmark Supreme Court ruling three decades ago bears striking similarities to the current moment — in which another conservative majority on the high court has been presented with an opportunity to potentially overturn Roe. But this time, the outcome could be far different.

» READ MORE: Leaked Supreme Court draft ruling on Roe v. Wade: What you need to know

On Monday, Politico released a leaked draft of the court’s still undecided ruling in Dobbs v. Jackson Women’s Health Organization — a challenge to a Mississippi law banning most abortions after 15 weeks of pregnancy — that would not only uphold the statute but also overturn Roe.

Authored by Alito — now a Supreme Court justice, 30 years after he weighed in on the Casey case as a judge on the Philadelphia-based U.S. Court of Appeals for the Third Circuit — the draft renews his call from his dissenting opinion in Casey that states should be allowed to decide for themselves whether to restrict abortion access.

» READ MORE: Live coverage: Supreme Court confirms leaked abortion ruling draft is authentic

“Roe was egregiously wrong from the start,” he wrote in the draft released Monday. “Roe and Casey have inflamed debate and deepened division.”

Here’s what you need to know about Planned Parenthood v. Casey — the Pennsylvania case that reaffirmed Roe’s essential holding of a constitutional right to have an abortion but also sowed the seeds for its unraveling:

In the 1980s, the Pennsylvania legislature passed and revised a law known as the Pennsylvania Abortion Control Act that instituted several new requirements before individuals could obtain abortions in the state. They included a 24-hour waiting period, parental consent for minors seeking to undergo such a procedure, and a spousal notification requirement.

Planned Parenthood led a coalition of plaintiffs who in 1990 sued Pennsylvania Gov. Bob Casey Sr., arguing that such restrictions were unconstitutional under the standard set by Roe in 1973

» READ MORE: How a proposed amendment to the state constitution could affect abortion access in Pennsylvania

And in 1992 after a series of lower-court decisions in Philadelphia, the case made its way to the Supreme Court, where abortion opponents were hopeful that a newly cemented eight-member, supermajority of Republican-appointed justices — including new Justices David Souter and Clarence Thomas — would use the case as an opportunity to revisit and overturn the court’s earlier findings in Roe.

» READ MORE: Opinion: I fought to preserve abortion rights in 1992. Here's why I'm terrified about the Supreme Court now.

In its ruling, authored by Republican-appointed Justices Sandra Day O’Connor, Anthony M. Kennedy, and Souter, the deeply divided court upheld nearly all the restrictions imposed by Pennsylvania’s law except for the spousal notification requirement.

But surprising many, O’Connor, Kennedy, and Souter declined to use the case as an opportunity to strike down Roe and instead did the opposite.

They reaffirmed the 1973 case’s central tenet that, despite the restrictions they were upholding, an individual’s right to choose to have an abortion before a fetus was viable was constitutionally protected.

They based their decision on the Supreme Court’s long-held practice of respecting its own earlier decisions in most instances. Straying from that principle, they wrote, risked undermining respect for the court and the rule of law.

“An entire generation has come of age free to assume Roe’s concept of liberty in defining the capacity of women to act in society and to make reproductive decisions,” they wrote.

They called on advocates on both sides of the abortion debate to view their ruling as the court’s final word on the legality of abortion.

Additionally, the ruling cemented the standard by which many future cases related to abortion rights would be judged — creating what is known as the “undue burden standard” for laws restricting abortion access. Essentially, it held that states could pass their own laws limiting abortion access except for when the purpose of those laws was to place “a substantial obstacle” in the path of a person seeking to abort a nonviable fetus.

While the Casey decision has been hailed for decades as a victory for abortion-rights advocates due to its underlining of the central tenets of Roe, it has also provided the legal framework under which many court rulings that followed upheld ever more restrictive state laws.

On its way to the Supreme Court in the early 1990s, the Casey case was reviewed by both a U.S. District judge in Philadelphia and the U.S. Court of Appeals for the Third Circuit, where Alito was serving as a circuit judge at the time.

A native of Hamilton Township, N.J., he’d joined the court just two years earlier. He was selected as part of a three-judge panel — along with Circuit Judges Walter King Stapleton and Collins J. Seitz — to hear the case on behalf of the appellate court.

Like the Supreme Court’s eventual ruling, the judges’ decision upheld many of the abortion restrictions imposed by the Pennsylvania law but struck down the spousal-notification requirement. Alito dissented, saying he believed Pennsylvania had a legitimate interest in requiring women to tell their husbands.

“Some married women are initially inclined to obtain an abortion without their husbands’ knowledge because of perceived problems — such as economic constraints, future plans, or the husband’s previously expressed opposition — that may be obviated by discussion prior to the abortion,” he wrote.

When the Supreme Court weighed in a year later, it rejected Alito’s reasoning.

“There are millions of women in this country who are victims of regular physical and psychological abuse at the hands of their husbands,” the justices wrote. “Should these women become pregnant, they may have very good reasons for not wishing to inform their husbands of their decision to obtain an abortion.”

O’Connor’s role in the Casey decision was hailed as one of her crowning achievements on the court when she retired in 2006.

President George W. Bush nominated Alito to replace her.

The draft majority opinion leaked Monday would strike down Casey and Roe. Alito called the reasoning behind both decisions “egregiously wrong.”

O’Connor, Kennedy, and Souter may have hoped their Casey ruling would finally put the question of abortion’s legality to rest, Alito wrote, but “as has become increasingly apparent in the intervening years, Casey did not achieve that goal.”

Alito criticized their decision, saying it relied too much on respecting the precedent of the 1973 decision when they should have first analyzed whether Roe was constitutionally sound. He described Casey’s “undue burden standard” by which new laws restricting abortion should be judged as both arbitrary and vague.

“We hold that Roe and Casey must be overruled,” he wrote. “The Constitution makes no reference to abortion and no such right is implicitly protected by any constitutional provision. … It’s time to heed the Constitution and return the issue of abortion to the people’s elected representatives.”

» READ MORE: Leaked Supreme Court draft ruling on Roe v. Wade: What you need to know

As Politico repeatedly stressed in its story Monday, the leaked opinion is a draft originally written in February and does not preclude the possibility that some justices might change their opinions or that the scope of the ruling could change before it is officially recorded by the court.

In fact, Casey provides a key lesson in how internal court wrangling among the justices can change over time.

When the justices held their conference on the case in the fall of 1991, they initially voted 5-4 to uphold the Pennsylvania law. Chief Justice William H. Rehnquist, writing for the majority, drafted an opinion that would have undercut Roe’s finding that access to an abortion was a constitutionally protected right, according to papers and memoirs released by several of the former justices in the years since.

But as that draft was circulating, O’Connor and Souter persuaded Kennedy to change his mind about overturning Roe, resulting in the decision that for decades has affirmed the constitutional right to obtain an abortion.