WASHINGTON -- Justice Ruth Bader Ginsburg, 80, vowed in an interview to stay on the Supreme Court as long as her health and intellect remained strong, saying she was fully engaged in her work as the leader of the liberal opposition on what she called "one of the most activist courts in history."
In wide-ranging remarks in her chambers on Friday that touched on affirmative action, abortion and same-sex marriage, Justice Ginsburg said she had made a mistake in joining a 2009 opinion that laid the groundwork for the court's decision in June effectively striking down the heart of the Voting Rights Act of 1965. The recent decision, she said, was "stunning in terms of activism."
Unless they have a book to sell, Supreme Court justices rarely give interviews. Justice Ginsburg has given several this summer, perhaps in reaction to calls from some liberals that she step down in time for President Obama to name her successor.
On Friday, she said repeatedly that the identity of the president who would appoint her replacement did not figure in her retirement planning.
"There will be a president after this one, and I'm hopeful that that president will be a fine president," she said.
Were Mr. Obama to name Justice Ginsburg's successor, it would presumably be a one-for-one liberal swap that would not alter the court's ideological balance. But if a Republican president is elected in 2016 and gets to name her successor, the court would be fundamentally reshaped.
Justice Ginsburg has survived two bouts with cancer, but her health is now good, she said, and her work ethic exceptional. There is no question, on the bench or in chambers, that she has full command of the complex legal issues that reach the court.
Her age has required only minor adjustments.
"I don't water-ski anymore," Justice Ginsburg said. "I haven't gone horseback riding in four years. I haven't ruled that out entirely. But water-skiing, those days are over."
Justice Ginsburg, who was appointed by President Bill Clinton in 1993, said she intended to stay on the court "as long as I can do the job full steam, and that, at my age, is not predictable."
"I love my job," she added. "I thought last year I did as well as in past terms."
With the departure of Justice John Paul Stevens in 2010, Justice Ginsburg became the leader of the court's four-member liberal wing, a role she seems to enjoy. "I am now the most senior justice when we divide 5-4 with the usual suspects," she said.
The last two terms, which brought major decisions on Mr. Obama's health care law, race and same-sex marriage, were, she said, "heady, exhausting, challenging."
She was especially critical of the voting rights decision, as well as the part of the ruling upholding the health care law that nonetheless said it could not be justified under Congress's power to regulate interstate commerce.
In general, Justice Ginsburg said, "if it's measured in terms of readiness to overturn legislation, this is one of the most activist courts in history."
The next term, which begins on Oct. 7, is also likely to produce major decisions, she said, pointing at piles of briefs in cases concerning campaign contribution limits and affirmative action.
There is a framed copy of the Lilly Ledbetter Fair Pay Act of 2009 on a wall in her chambers. It is not a judicial decision, of course, but Justice Ginsburg counts it as one of her proudest achievements.
The law was a reaction to her dissent in Ledbetter v. Goodyear Tire and Rubber Company, the 2007 ruling that said Title VII of the Civil Rights Act of 1964 imposed strict time limits for bringing workplace discrimination suits. She called on Congress to overturn the decision, and it did.
"I'd like to think that that will happen in the two Title VII cases from this term, but this Congress doesn't seem to be able to move on anything," she said.
"In so many instances, the court and Congress have been having conversations with each other, particularly recently in the civil rights area," she said. "So it isn't good when you have a Congress that can't react."
The recent voting rights decision, Shelby County v. Holder, also invited Congress to enact new legislation. But Justice Ginsburg, who dissented, did not sound optimistic.
"The Voting Rights Act passed by overwhelming majorities," she said of its reauthorization in 2006, "but this Congress I don't think is equipped to do anything about it."
Asked if she was disappointed by the almost immediate tightening of voting laws in Texas and North Carolina after the decision, she chose a different word: "Disillusioned."
The flaw in the court's decision, she said, was to conclude from the nation's progress in protecting minority voters that the law was no longer needed. She repeated a line from her dissent: "It is like throwing away your umbrella in a rainstorm because you are not getting wet."
Chief Justice John G. Roberts Jr. wrote the majority opinion, and he quoted extensively from a 2009 decision that had, temporarily as it turned out, let the heart of the Voting Rights Act survive. Eight members of the court, including Justice Ginsburg, had signed the earlier decision.
On Friday, she said she did not regret her earlier vote, as the result in the 2009 case was correct. But she said she should have distanced herself from the majority opinion's language. "If you think it's going to do real damage, you don't sign on to it," she said. "I was mistaken in that case."
Some commentators have said that the two voting rights decisions are an example of the long game Chief Justice Roberts seems to be playing in several areas of the law, including campaign finance and affirmative action. Justice Ginsburg's lone dissent in June's affirmative action case, leaving in place the University of Texas' admissions plan but requiring lower courts to judge it against a more demanding standard, may suggest that she is alert to the chief justice's apparent strategy.
Justice Ginsburg is by her own description "this little tiny little woman," and she speaks in a murmur inflected with a Brooklyn accent. But she is a formidable force on the bench, often asking the first question at oral arguments in a way that frames the discussion that follows.
She has always been "a night person," she said, but she has worked even later into the small hours since her husband, Martin D. Ginsburg, a tax lawyer, chef and wit, died in 2010. Since then, she said, there is no one to call her to bed and turn out the lights.
She works out twice a week with a trainer and said her doctors at the National Institutes of Health say she is in fine health.
"Ever since my colorectal cancer in 1999, I have been followed by the N.I.H.," she said. "That was very lucky for me because they detected my pancreatic cancer at a very early stage" in 2009.
Less than three weeks after surgery for that second form of cancer, Justice Ginsburg was back on the bench.
"After the pancreatic cancer, at first I went to N.I.H. every three months, then every four months, then every six months," she said. "The last time I was there they said come back in a year."
Justice Ginsburg said her retirement calculations would center on her health and not on who would appoint her successor, even if that new justice could tilt the balance of the court and overturn some of the landmark women's rights decisions that are a large part of her legacy.
"I don't see that my majority opinions are going to be undone," she said. "I do hope that some of my dissents will one day be the law."
She said that as a general matter the court would be wise to move incrementally and methodically. It had moved too fast, she said, in Roe v. Wade, the 1973 decision that established a constitutional right to abortion. The court could have struck down only the extremely restrictive Texas law before it.
"I think it's inescapable that the court gave the anti-abortion forces a single target to aim at," she said. "The unelected judges decided this question for the country, and never mind that the issue was in flux in the state legislatures."
The question of same-sex marriage is also in flux around the nation. In June, the court declined to say whether there was a constitutional right to same-sex marriage, allowing the issue to percolate further. But Justice Ginsburg rejected the analogy to the lesson she had taken from the aftermath of the Roe decision.
"I wouldn't make a connection," she said.
The fireworks at the end of the last term included three dissents announced from the bench by Justice Ginsburg. Such oral dissents are rare and are reserved for major disagreements.
One was a sharp attack on Justice Samuel A. Alito Jr.'s majority opinion in a job discrimination case, and he made his displeasure known, rolling his eyes and making a face.
Justice Ginsburg said she took it in stride. "It was kind of a replay of the State of the Union, when he didn't agree with what the president was saying" in 2010 about the Citizens United decision. "It was his natural reaction, but probably if he could do it again, he would have squelched it."
This article originally appeared in The New York Times.