WASHINGTON — In a series of stunning decisions over the past two weeks, Chief Justice John G. Roberts Jr. has voted to expand L.G.B.T.Q. rights, protect the young immigrants known as Dreamers and strike down a Louisiana abortion law. In all three decisions, he voted with the court’s four-member liberal wing.
Those decisions heartened progressives and infuriated the chief justice’s usual conservative allies. But those reactions obscured a larger truth about Chief Justice Roberts: 15 years into his tenure, he now wields a level of influence that has caused experts to hunt for historical comparisons.
“Roberts is not only the most powerful player on the court,” said Lee Epstein, a law professor and political scientist at Washington University in St. Louis. “He’s also the most powerful chief justice since at least 1937.”
An incrementalist and an institutionalist, the chief justice generally nudges the court to the right in small steps, with one eye on its prestige and legitimacy. He is impatient with legal shortcuts and, at only 65, can well afford to play the long game.
Chief Justice Roberts has replaced Justice Anthony M. Kennedy, who retired in 2018, as the member of the court at its ideological center, and his vote is now the crucial one in closely divided cases. To be both the chief justice and the swing vote confers extraordinary power.
But his pivotal role on the court could be fleeting. Were President Trump able to appoint a replacement for Justice Ruth Bader Ginsburg, who is 87, or Justice Stephen G. Breyer, who is 81, the chief justice would almost certainly be outflanked by a conservative majority on his right.
And if Joseph R. Biden Jr. wins the presidency, he may have fewer opportunities to reshape the court in the short term, as the oldest member of the court’s conservative wing, Justice Clarence Thomas, is 72, which is relatively young by the standards of the court.
But for now, Chief Justice Roberts assigns the majority opinion when he is in the majority, which these days is almost always. He uses that power strategically, picking colleagues likely to write broadly or narrowly and saving important decisions for himself.
In his first 14 terms, he was in the majority about 88 percent of the time. So far this term, that number has shot up to 98 percent, Professor Epstein found. “Even more stunning,” she said, “is that Roberts voted with the majority in 96 percent of the non-unanimous decisions, compared to his average of 80 percent. This is the best showing by a chief justice since at least the 1953 term.”
But this may be the most striking statistic: He has been in the majority in every one of the 10 rulings decided by 5-to-4 or 5-to-3 votes so far this term. No chief justice has been in the majority in every closely divided case over an entire term since Chief Justice Charles Evans Hughes in the term that ended in 1938 — and that was in only four cases.
Chief Justice Roberts has spoken admiringly of Chief Justice Hughes and his deft management of a clash with President Franklin D. Roosevelt. It arose in 1937, when Roosevelt, unhappy with Supreme Court decisions striking down his New Deal programs, announced a plan to add justices to the court.
“One of the greatest crises facing the Supreme Court since Marbury v. Madison was F.D.R.’s court-packing plan,” Chief Justice Roberts said in 2015 at New York University, “and it fell to Hughes to guide a very unpopular Supreme Court through that high-noon showdown against America’s most popular president since George Washington.”
“There are things to learn from it,” Chief Justice Roberts said, and he has seemed to apply those lessons to his relationship with Mr. Trump, who has attacked the very idea of judicial independence.
Chief Justice Roberts was appointed by President George W. Bush in 2005, and he was, back then, thought to be a reliable product of the conservative legal movement. Over the years, he occasionally disappointed his supporters and allies, notably in twice voting to sustain the Affordable Care Act and in rejecting the Trump administration’s efforts to add a question on citizenship to the census.
But those disappointments do not compare with the fury that followed the recent decisions. Conservatives said the chief justice has abandoned principle in an effort to protect the court’s reputation — and his own — from accusations that it is a political institution.
“Americans hoping for justice for women and unborn babies were let down again today by John Roberts,” said Senator Tom Cotton, Republican of Arkansas. “The chief justice may believe that he’s protecting the institutional integrity of the court, but in reality, his politicized decision-making only undermines it.”
Conservatives said they suspected the chief justice was acting at least partly based on a distaste for Mr. Trump, who has for years lashed out at federal judges who rule against him and his policies. They cited the chief justice’s majority opinions rejecting the administration’s rationales in the cases on the census and the Dreamers.
A pair of cases concerning Mr. Trump’s efforts to block disclosure of his financial records are among those that remain to be decided by the court this term. They will test Chief Justice Roberts’s leadership, and his votes in them will add important details to the portrait of him that has emerged thus far.
Chief Justice Roberts has tangled with the president before, issuing an extraordinary statement in 2018 after Mr. Trump criticized a ruling from an “Obama judge.”
“We do not have Obama judges or Trump judges, Bush judges or Clinton judges,” the chief justice said. “What we have is an extraordinary group of dedicated judges doing their level best to do equal right to those appearing before them. That independent judiciary is something we should all be thankful for.”
In other settings, the chief justice has insisted that the justices do not act as partisans. “We don’t work as Democrats or Republicans,” he said in 2016.
Richard J. Lazarus, a law professor at Harvard, said Monday’s abortion decision vindicated Chief Justice Roberts’s statements.
“The chief is sending a broader message to both parties, and this time in this case it is the Republicans who take the hit,” Professor Lazarus said. “But the message would be the same if it were the Democrats and their favored position had lost.”
The message was this, Professor Lazarus said: “You cannot expect us to behave like partisan legislators.”
The abortion case concerned a Louisiana law that was essentially identical to one from Texas that the court had struck down just four years ago, before Mr. Trump appointed two new justices. In dissent in 2016, Chief Justice Roberts had voted to uphold the Texas law.
Professor Lazarus said he suspected the chief justice was offended by the idea that a change in the composition of the court should warrant a different outcome in what was, at bottom, the identical case.
This term, Professor Epstein found, Chief Justice Roberts has voted with liberal and conservative justices at roughly equivalent rates.
“In a day and age of ‘fear and loathing’ between opposing partisans,” she said, “this is pretty extraordinary.”
Melissa Murray, a law professor at New York University, said she had considered alternative explanations for Chief Justice Roberts’s vote in the abortion case. One was that he was “a closet liberal.” The other was that he was “a deep-seated institutionalist intent on preserving the court’s legitimacy and rule-of-law values.”
She said the second explanation was more likely to be true, though she said his concurring opinion in the abortion case had in some ways limited the force of the 2016 precedent he said he was upholding.
Mike Davis, a former Senate Judiciary Committee counsel who is now head of the conservative Article III Project, said he was puzzled by Chief Justice Roberts’s votes.
“The chief rules on these cases in such a way where he believes he is protecting the integrity of the Supreme Court,” Mr. Davis said. “And only the chief understands the method to this madness.”
But he added that the rulings would motivate conservative voters in the coming election to back Mr. Trump and Republican Senate candidates in hopes of cementing a more reliable conservative majority on the court.
“Over the next four years, the president of the United States could appoint four or more justices to the Supreme Court,” Mr. Davis said. “And that is why it is so critically important that conservatives turn out and vote.”
Professor Lazarus said that sort of thinking missed a distinction between politics and law.
“The chief’s clear message is that is not how justices do their work,” he said. “It is a shot across the bow at presidential candidates who campaign with lists of nominees based on the assumption that, if confirmed, they will of course necessarily vote based on the preferences of the majority who supported that candidate.”