WASHINGTON—Chief Justice John Roberts has long pursued two goals on the Supreme Court: move its jurisprudence incrementally to the right and insulate the institution from the heat of Washington politics.

The court’s historic decision on Friday to overturn Roe v. Wade shows how hard that has become.

The court overturned the 1973 precedent that established a constitutional right to an abortion, in a decision written by his fellow Republican-appointed colleague, Justice Samuel Alito, and joined by the court’s four other conservatives.

The decision in Dobbs v. Jackson Women’s Health Organization left Chief Justice Roberts alone with his more incremental approach to the case. He expressed support in a concurring opinion for the Mississippi law banning abortions after 15 weeks, the proximate issue of the court’s case. But he sharply disagreed with his fellow conservative justices’ wholesale elimination of the abortion right, which had been in place for almost a half-century and affirmed in a post-Roe case, Planned Parenthood of Southeastern Pennsylvania v. Casey, in 1992.

“The Court’s decision to overrule Roe and Casey is a serious jolt to the legal system—regardless of how you view those cases,” the chief justice wrote.“A narrower decision…would be markedly less unsettling, and nothing more is needed to decide this case.”

Artemus Ward, a professor at Northern Illinois University whose research focuses on the Supreme Court, said Chief Justice Roberts was now marginalized “and he’s calling out Alito and the other conservatives, saying, ‘You didn’t need to do this. You didn’t need to go this far.’”

The chief justice was no less disturbed by the position of the three liberals on the bench. “Both the Court’s opinion and the dissent display a relentless freedom from doubt on the legal issue that I cannot share,” he wrote.

The split on Roe v. Wade illustrates the diverging approaches to jurisprudence taken by Chief Justice Roberts, 67 years old, and Justice Alito, 72, since 2005, the year they were both nominated for the court by former President George W. Bush.

“Throughout their careers, Chief Justice Roberts has played the long game, while Justice Samuel Alito prefers to move fast and break things, urging maximalist rulings that move the law far to the right,” said David Gans, a lawyer at Constitutional Accountability Center, a left-leaning think tank. “These differences play out in Dobbs.”

When Justice Sandra Day O’Connor retired from the Supreme Court in 2005, Messrs. Roberts and Alito, both sitting on intermediate appeals courts, were on Mr. Bush’s shortlist of potential justices.

Karl Rove, a senior Bush adviser, wrote in a 2010 book that Mr. Roberts came across during an early job interview as “restrained and guarded.” Mr. Bush, impressed by Mr. Roberts’s precision and intelligence, concluded he would be a natural “leader on the Court,” Mr. Rove wrote.

Mr. Alito, on the other hand, came across as “painfully shy,” Mr. Rove recalled, adding: “But boy, was he smart,” noting the judge’s ability to explain complicated legal concepts in a clear way.

When Chief Justice William Rehnquist died a few weeks after Mr. Roberts had gotten the nod for Justice O’Connor’s seat, Mr. Bush nominated him instead for the chief position.

After the president’s nomination of his friend and White House counsel, Harriet Miers, faltered among criticism particularly from conservatives, Mr. Bush settled on Mr. Alito to fill Justice O’Connor’s seat. The move drew praise from antiabortion advocates who had pushed for a staunch conservative.

During their first years on the court, Chief Justice Roberts and Justice Alito were closely aligned.

In 2007, they joined a majority opinion that upheld a federal ban on late-term abortion, even though seven years earlier the court had struck down an almost identical state law as a violation of Roe. That same year, in another 5-4 case, the two justices both said race can’t be a factor in the assignment of children to public schools.

Liberal Justice Stephen Breyer, finding himself on the losing side of a number 5-4 decisions, noted the impact his new conservative colleagues. “It is not often in the law that so few have so quickly changed so much,” he wrote in summarizing his dissent to that school decision.

Sen. Chuck Schumer (D., N.Y.) said in a 2007 speech that Democrats had been “duped” by Chief Justice Roberts’s lofty words about stability and incrementalism during his confirmation hearings. “We were promised an era of gentility and consensus if the affable John Roberts were confirmed as Chief Justice,” Mr. Schumer said. “There is no doubt we were hoodwinked.”

The chief justice reframed his legacy, however, with his 2012 ruling that largely upheld then-President Barack Obama’s Affordable Care Act, the law known as Obamacare.

Liberals hailed the decision, though seasoned court-watchers saw it as an act of pragmatism. By deferring to Congress, Chief Justice Roberts avoided roiling a major part of the U.S. economy and sidestepped a fight that could have harmed public perceptions of the court.

The pivotal vote ushered in an era during which the chief justice joined his liberal colleagues in occasional high-profile rulings, while still incrementally moving the court to the right on many fronts. In 2019, the chief justice blocked the Trump’s administration’s effort to include a question on citizenship in the 2020 census. Then in the span of two weeks in 2020, he voted to strike down a Louisiana abortion law, protect the young immigrants known as “Dreamers,” and prohibit employment discrimination based on sexual orientation or gender identity—each time joining the court’s liberals.

“Roberts picks his spots,“ Mr. Ward said. ”In a high-profile case, he will often move to the center. In a high-profile case, he’s going to be more concerned about seeking consensus.”

While the chief justice was polishing his reputation as a consensus-seeker, Justice Alito was burnishing his conservative credentials—and making known his displeasure with Chief Justice Roberts’s jurisprudence.

In an unusually political speech to the Federalist Society in 2020, Justice Alito expressed dismay at the state of college campuses and workplaces, saying conservatives were being maligned for holding views that recently had been mainstream.

“You can’t say that marriage is a union between one man and one woman” any more, Justice Alito said. “Until very recently, that’s what the vast majority of Americans thought. Now it’s considered bigotry.”

President Donald Trump with Justice Samuel Alito in 2019. Photo: Carolyn Kaster/Associated Press

Tensions between the two justices were evident in June 2021, when Chief Justice Roberts wrote a narrowly drawn majority opinion in a religious-freedom case.

“The Court has emitted a wisp of a decision that leaves religious liberty in a confused and vulnerable state,” Justice Alito wrote in a concurring opinion. “Those who count on this Court to stand up for the First Amendment have every right to be disappointed—as am I.”

The chief justice’s decision for the majority, Justice Alito wrote, “might as well be written on the dissolving paper sold in magic shops.”

The two men’s split on the fate of Roe v. Wade puts those differences in starker relief than ever, and it leaves in peril the chief justice’s efforts to use his position to forge a court based in consensus and continuity.