WASHINGTON » The stunning series of liberal decisions delivered by the Supreme Court this term was the product of discipline on the left side of the court and disarray on the right.

In case after case, including blockbusters on same-sex marriage and President Barack Obama’s health care law, the court’s four-member liberal wing, all appointed by Democratic presidents, managed to pick off one or more votes from the court’s five conservative justices, all appointed by Republicans.

They did this in large part through rigorous bloc voting, making the term that concluded Monday the most liberal one since the Warren court in the late 1960s, according to two political-science measurements of court voting data.

"The most interesting thing about this term is the acceleration of a long-term trend of disagreement among the Republican-appointed judges, while the Democratic-appointed judges continue to march in lock step," said Eric Posner, a law professor at the University of Chicago.

Many analysts credit the leadership of Justice Ruth Bader Ginsburg, the senior member of the liberal justices, for leveraging their four votes. "We have made a concerted effort to speak with one voice in important cases," she said in an interview last year.

The court’s conservatives, by contrast, were often splintered, issuing separate opinions even when they agreed on the outcome. The conservative justices, for instance, produced more than 40 dissenting opinions, the liberals just 13.

The divisions on the right, Posner said, may have occurred in part because the mix of cases reaching the court has invited a backlash. "Conservative litigators who hope to move the law to the right by bringing cases to the Supreme Court have overreached," he said. "They are trying to move the law farther right than Kennedy or Roberts think reasonable."

For example, in King v. Burwell, the case brought by groups hostile to the Affordable Care Act, Chief Justice John G. Roberts Jr. and Justice Anthony M. Kennedy joined the court’s four liberals in rejecting the challenge to health insurance subsidies provided through federal exchanges. Justices Antonin Scalia, Clarence Thomas and Samuel A. Alito Jr. dissented.

In addition, Posner said, the conservative justices are airing real jurisprudential disagreements. "Kennedy, Roberts and Alito’s pragmatism contrasts with the formalism of Scalia and Thomas, for example," he said.

Lee Epstein, a law professor and political scientist at Washington University in St. Louis, said: "The Republicans can’t seem to agree even when they agree." She added that "the chief justice has a much tougher task" than Ginsburg does.

David A. Strauss, a law professor at the University of Chicago, said the cases the court agreed to hear this past term might have created a misperception about how liberal it has become. "It’s still a conservative court — just not as conservative as some had hoped and some had feared," he said. "King might never even have been brought if the court, or at least some justices, had not given signals that they were receptive to claims like that."

The term was not uniformly liberal, of course. On Monday alone, the court ruled against death row inmates in a case on lethal injections and against the Obama administration in a case on environmental regulations.

The Obama administration, though, found an unlikely ally in the court in major cases, said Pratik A. Shah, a lawyer with Akin Gump Strauss Hauer & Feld. "Not many imagined a few years ago," Shah said, "that this court, rather than Congress, would become the more effective venue for furthering the administration’s priorities."

When the administration ended up on the losing side, it was often because it took a conservative position, particularly in criminal cases, said Adam Winkler, a law professor at the University of California, Los Angeles.

"The administration most often lost the court because it couldn’t hold the liberals," Winkler said. "The administration’s positions in the Supreme Court were too conservative. Shockingly, the Supreme Court may have been more liberal than the Obama administration this term." This was so, he said, in cases involving drugs, guns, searches and threats posted on Facebook.

When the four liberal members of the court — Ginsburg, Stephen G. Breyer, Sonia Sotomayor and Elena Kagan — achieved a majority, they were often happy to let others do the talking.

"I was struck by the discipline of the liberal wing — both in sticking together and in suppressing the urge any of them may have felt to write separately," said Michael Dorf, a law professor at Cornell. This produced strong and united opinions, he said, from Kennedy in Obergefell v. Hodges, the same-sex marriage case, and from Roberts in the health care case.

Dissenting in Obergefell, Scalia accused the court’s liberals of a sort of intellectual dishonesty in joining Kennedy’s opinion, which he charged sacrificed legal rigor for soaring language. "If, even as the price to be paid for a fifth vote, I ever joined an opinion for the court" that included such vague passages, he wrote, quoting one, "I would hide my head in a bag."

Kennedy, the member of the court at its ideological center, did his part in moving the court to the left. As usual, he was in the majority in most of the 19 decisions decided by 5-4 votes.

Thirteen of those rulings split along the usual lines, with Kennedy joining either the court’s four more liberal members or its four more conservative ones. In previous terms, he leaned right in such cases about two-thirds of the time. This time around, he voted with the liberals eight times and with the conservatives five.

In major cases, the court seemed to capture the spirit of the time, notably in establishing a constitutional right to same-sex marriage as a majority of Americans came to embrace it. Ginsburg seemed to anticipate and explain the ruling in remarks this month at the American Constitution Society, a liberal legal group. "The court is not in a popularity contest, and it should never be influenced by today’s headlines, by the weather of today," she said. "Inevitably, it will be affected by the climate of the era."

Samuel Issacharoff, a law professor at New York University, said the court had played a traditional and proper role in the case. "The speed of the shifting societal consensus on same-sex marriage is astonishing," he said. "The court protecting the emerging national consensus is not."

A second 5-4 decision, allowing Texas to reject specialty license plates bearing the Confederate battle flag, was issued the morning after the shootings in Charleston, South Carolina, started a national debate about the meaning of that symbol. The timing was coincidence, and the vote was close. The liberals, as usual, voted as a group — but they were joined by Thomas in a rare alliance.

This term may have been an anomaly, and the next one may shift back to the right. The justices have already agreed to hear cases on affirmative action and the meaning of "one person, one vote," and they are likely to hear a major abortion case. Last term, the court issued unanimous decisions in about two-thirds of its case, a modern record. This term, the number dropped to about 40 percent, a little lower than the average in recent terms.

But the court remained united in cases involving religion, issuing unanimous rulings in favor of a Muslim inmate in an Arkansas prison who wanted to grow a beard and an Arizona church that challenged a town ordinance limiting the size of signs announcing services.

Business groups had a mixed record, winning 12 of the 22 cases in which they faced individuals or the government. "This term’s business decisions should put an end to the persistent theory that the Roberts court is reflexively biased in favor of corporate interests," said Lauren R. Goldman, a lawyer with Mayer Brown.

Moreover, she said, many of the business victories were narrow. "On the other side of the ledger," she said, "the court handed the business community several substantial losses." Among the setbacks, she said, were victories for plaintiffs in employment discrimination cases and a broad interpretation of the scope of the Fair Housing Act.

Overall, though, the story of the last nine months at the Supreme Court was of leftward movement.

"This term feels just huge," said Lisa S. Blatt, a lawyer with Arnold & Porter who has argued more than 30 cases in the Supreme Court and studied its work for two decades. "It’s clearly the most liberal term I’ve seen since I’ve been watching the court."

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