WASHINGTON — This past summer, the fate of abortion rights in the country hung by a thread.
The Supreme Court, which saw its socially moderate swing vote Anthony Kennedy retire in 2018, appeared poised to uphold a Louisiana law that sharply curtailed access to abortions — a decision that would likely set off a cascade of similar laws across the country.
Instead, conservative Chief Justice John Roberts, who had voted in favor of allowing a similar measure in Texas just four years earlier, changed his mind. He joined the court’s four liberals to strike down the Louisiana law, citing the earlier precedent and giving abortion rights' activists a surprising victory — and temporary relief.
That relief has turned to dread among liberals, now that President Trump, aided by a Senate Republican majority that has reversed its earlier position on election-year nominees, seems all but certain to replace one of those liberals, Ruth Bader Ginsburg, with a conservative stalwart he plans to announce on Saturday.
If confirmed, that replacement would give conservatives a rock solid 6-3 advantage on a Supreme Court that already leaned sharply to the right, with the potential to reshape abortion rights, affirmative action, policing, and many other crucial issues over the coming decades while erecting a judicial barrier to attempts by future Democratic administrations to enact bold liberal policies.
An enhanced conservative majority also would mean an end to the temporary role Roberts took on this past year as a sometimes swing vote preventing aggressive moves that might make the public see the court as overtly political, such as ending the deferred action program for young immigrants or chipping away at Roe v. Wade.
“If President Trump succeeds in replacing Justice Ginsburg, it would be the most consequential and transformative appointment in the history of the court,” said Jonathan Turley, a conservative legal scholar at George Washington University Law School. “There are a very significant number of cases that are dangling by a 5-4 majority.”
The most noteworthy of those cases: Roe v. Wade.
Federal appellate Judge Amy Coney Barrett, who is at the top of Trump’s short list for the vacancy, has already indicated she disagrees with the foundations of the Roe decision. And Justice Brett Kavanaugh’s vote in favor of Louisiana’s restrictive law has shown he is not likely to be a swing vote on abortion matters, unlike Kennedy, whose seat he filled as Trump’s second court nominee.
“That case shows how hard we had to work just to win the same issue in the Supreme Court we had won two years before,” said Nancy Northrup, the head of the Center for Reproductive Rights, which represented Louisiana’s abortion providers.
A third Trump-appointed justice, both conservative and liberal legal scholars agree, puts Roe v. Wade fully on notice, capping decades of effort by antiabortion activists.
“Nothing of significance would be left of Roe v. Wade, whether they expressly overturn it or crush it in two or three blows — it would be gone,” said Laurence Tribe, a liberal constitutional law scholar at Harvard Law School.
Another legal issue that has long been targeted by some conservatives may also be in jeopardy — affirmative action. In 2016, the court narrowly decided to allow the University of Texas to continue to use race as part of its admissions process, with Kennedy as the swing vote. Roberts opposed the decision.
“One big limitation of federal power could be with respect to affirmative action,” predicted Richard Friedman, an expert on Supreme Court history at the University of Michigan. “That’s an area where the chief justice has been vigorously against.” Such a decision might cut back more on the use of race as a factor in college admissions, or bar it altogether.
A 6-3 conservative court also would likely reaffirm the right of the state to use the death penalty despite objections that it amounts to cruel and unusual punishment, Turley predicted, and back law enforcement in disputes over whether police shootings amount to unreasonable search and seizures.
“The expectation is that this new addition will give a static and stable majority in favor of law enforcement on issues of that kind,” Turley said.
The court is already very conservative on matters of gun rights and campaign finance, as evidenced in the Citizens United decision striking down a campaign finance law as a violation of free speech. A sixth conservative vote would solidify that conservative drift, but may not tilt the outcome from the previous court.
Some progressives predict the emboldened 6-3 Supreme Court would take an aggressive posture against any future Democratic administrations, striking down social welfare programs or larger attempts to combat climate change as governmental overreach. That would mimic the Supreme Court of the 1930s, which frequently butted heads with President Franklin D. Roosevelt over his bid to set a minimum wage and other New Deal-era economic reforms. (The standoff ended after Roosevelt threatened to expand the number of seats on the court.)
“It would be the most right wing court in the history of the republic,” Tribe said. “Far more conservative even than the court that Roosevelt confronted when he came into power.”
Democratic lawmakers have seized that argument, painting Trump’s appointment as a mortal threat to the Affordable Care Act, which faces a court challenge this fall that will be heard a week after the presidential election. Trump’s nominee could be confirmed and seated in time to hear the case.
“The Republicans hope they can get in one more justice, which might permit them to do something they can’t do through Congress, and that is take away health care for tens of millions of people,” Massachusetts Senator Elizabeth Warren said on Tuesday.
But some legal scholars said they believe it’s unlikely that the future court would take the aggressive posture of the 1930s, which is sometimes referred to as the Lochner era, by repeatedly striking down federal laws passed by Democratic Congresses.
“I don’t see them going back to the Lochner world,” said Geoffrey Stone of the University of Chicago. “That’s been discredited.”
Stone added that the court would still be the most conservative one since the 1930s, even if they take a less confrontational posture than that court did.
There’s also a chance that the Affordable Care Act would survive, at least this time around, even if facing six conservative justices.
The case revolves around the highly technical issue of severability, or whether a law is still enforceable even after a piece of it — in this case, the individual mandate that required most Americans to have health insurance or pay a penalty — has been stripped away. In another case involving severability, Kavanaugh ruled in favor of the legality of the rest of a statute, suggesting he could do so again. Roberts has repeatedly ruled in favor of the legality of the Affordable Care Act.
With Roberts no longer able to join four liberals and swing decisions, Democrats must now hope that Kavanaugh and Neil Gorsuch — Trump’s first court nominee — may become the new swing votes in high profile cases compared with justices Clarence Thomas and Samuel Alito, who have a longer track record of conservative rulings. It’s a sign of the entirely new context the court is entering.
“We are confronting a world where Gorsuch and Kavanaugh will look like moderates,” Tribe said.
Jess Bidgood of the Globe staff contributed to this report.