WASHINGTON – Over her 86½ years on earth, Ruth Bader Ginsburg has been lauded as a women's rights pioneer, a Supreme Court justice and a cultural icon. These days, she receives hearty ovations just for staying on the job.

To satisfy some of her liberal allies, she must do that for at least another 16 months.

Fresh off three weeks of radiation treatment for her fourth bout with cancer, the woman fondly known as the "Notorious RBG" is traveling the nation giving speeches, staging conversations and accepting awards and honorary degrees. By demonstrating her vitality before adoring audiences, she hopes to tamp down concerns about her longevity.

"As cancer survivors know, that dread disease is a challenge, and it helps to know that people are rooting for you. Now, it's not universal," she quipped Thursday night at the famed 92nd Street Y in New York City. She vowed to stay on the job "as long as I'm healthy and mentally agile."

The concerns are based on the political calendar. Ginsburg must remain on the nation's highest court at least until January 2021 to avoid giving President Donald Trump and a Republican-controlled Senate the opportunity to replace her. Such a doomsday scenario for liberals would give conservatives a 6-3 hold on the high court – solidifying their majority, perhaps for decades to come.

Currently divided 5-4 and with John Roberts in the chief justice's chair, the Supreme Court has been less reliable than conservatives would like. With the help of Roberts or another conservative justice during the last term, the court's four liberals held sway in as many 5-4 decisions as their counterparts.

More:Conservatives' takeover of Supreme Court stalled by John Roberts-Brett Kavanaugh bromance

But add a sixth conservative justice and "it becomes so much more difficult," says Erwin Chemerinsky, dean of the University of California-Berkeley School of Law, who caught flak in 2014 for suggesting Ginsburg should step down while President Barack Obama and a Senate Democratic majority could have replaced her.

If Democrats eventually prevail in confirming a liberal-leaning justice to their liking, Chemerinsky says, "This could be the swing vote down the road."

Ginsburg's predicament is similar to that faced by the court's last civil rights pioneer, Associate Justice Thurgood Marshall, in 1991. With his health declining as he approached his 83rd birthday, he retired during the third year of Republican George H.W. Bush's presidency. The New York Times headline blared: "Marshall retires from high court; blow to liberals."

Marshall ultimately lived four days into the administration of Democratic President Bill Clinton. But by then his seat was held by Associate Justice Clarence Thomas, still the court's most conservative member.

Ginsburg has shown no similar signs of "coming apart," as Marshall described himself in a calamitous 1991 press conference, though she did miss the first oral arguments of her career in January while recovering from lung cancer surgery.

The lone statement issued by the court after her latest bout with pancreatic cancer was upbeat. "The tumor was treated definitively and there is no evidence of disease elsewhere in the body," it said. "Justice Ginsburg will continue to have periodic blood tests and scans. No further treatment is needed at this time."

Crisscrossing the country

The statement was issued Aug. 23, and three days later Ginsburg was at the University of Buffalo to receive an honorary degree and speak at several events. That was a warm-up act for her visit to North Little Rock, Ark., the following week, where she received a standing ovation from a crowd estimated at 16,000, including many in "Notorious RBG" T-shirts.

"We all hope that she will stay on that court forever," former President Bill Clinton, who nominated her to the Supreme Court in 1993, said by way of introduction.

For her part, Ginsburg was more circumspect. "I’m pleased to say I am feeling very good tonight," she said.

Then it was on to the University of Chicago and Georgetown University Law Center the following week, and two appearances in her native New York City this week, where she took on directly the critique that she should have stepped down years ago.

“When that suggestion is made, I ask the question: Who do you think that the president could nominate that could get through the Republican Senate that you would prefer to have?" she said Wednesday night at the Yale Club, according to CNN.

But Democrats controlled the Senate in 2014, when Chemerinsky started the drumbeat with a Los Angeles Times column. "Justice Ruth Bader Ginsburg should retire from the Supreme Court after the completion of the current term in June," he wrote that March. "Only by resigning this summer can she ensure that a Democratic president will be able to choose a successor who shares her views and values."

Ginsburg resumes her national hopscotching tour Monday at Meredith College in Raleigh, N.C., where she will appear before about 1,600 fans. The following week, she will be at Amherst College in western Massachusetts.

The court's 2019 term begins Oct. 7, briefly keeping Ginsburg in the nation's capital, where her latest accolade was a two-story mural unveiled Monday on a downtown D.C. building. When two weeks of oral arguments are completed, she is scheduled to travel cross country to California.

"It's a travel schedule that would exhaust the rest of us," says Marge Baker, executive vice president of the liberal group People for the American Way. “This is a statement that’s she’s making, and she seems to draw energy from it.”

For years, Ginsburg has traveled and spoken publicly more than most of her colleagues. Before Associate Justice Antonin Scalia's death in 2016, the two ideological opposites occasionally made joint appearances that called attention to their longtime friendship. Ginsburg has made more than 170 public appearances in the last five years; only Associate Justice Sonia Sotomayor has done more.

"When I am active, I am much better than when I am just lying about feeling sorry for myself," Ginsburg said at the Yale Club event. "The necessity to get up and go is stimulating."

The most deadly cancer

Before her latest cancer was diagnosed, Ginsburg said she hoped to stay on the bench for at least five more years, noting that Associate Justice John Paul Stevens served until age 90. Stevens died in July at 99.

The latest health scare is particularly worrisome to many because it's her second bout with pancreatic cancer. The average five-year survival rate is 9%, lowest of all cancers. But Ginsburg has lived 10 years since her first bout.

The Pancreatic Cancer Action Network's website lists the names of public figures whose lives have been impacted by pancreatic cancer. The list includes 16 survivors such as opera singer Marilyn Horne, whose vow to live following her 2005 diagnosis Ginsburg admires. But it also names more than 250 public figures who succumbed to the disease.

Julie Fleshman, the network's president and CEO, says the three weeks of radiation Ginsburg received at Memorial Sloan Kettering Cancer Center in New York is the go-to treatment for small, localized tumors. A more serious form of the cancer would have called for surgery or further treatment, she says.

The justice's first major health scare was colon cancer in 1999. Chemotherapy and radiation left her depleted, so her late husband Martin convinced her to get a personal trainer. She has worked out twice a week ever since.

More:Squat, lift, kick, curl: Justice Ginsburg's workout is tough and it left me exhausted

Her first bout with pancreatic cancer in 2009 was caught early following a routine blood test, and she made a full recovery. She received a stent in a heart procedure in 2014. Then last November, she fell in her Supreme Court chambers and fractured three ribs, forcing her to miss new Associate Justice Brett Kavanaugh's investiture ceremony.

By then, her supporters were increasingly rattled. Twitter was flooded with good wishes as well as medical offers.

"Ruth Bader Ginsberg (sic) can have my ribs," actress and #MeToo activist Alyssa Milano tweeted. "And my kidneys and a lung. And anything else she needs."

The fall proved fortuitous, because it enabled doctors to find and remove two malignant nodules from her left lung. To recover from surgery, Ginsburg was forced to miss two weeks of oral argument in January – the first time she's been absent from the bench.

Her latest cancer has not slowed Ginsburg down, much to her supporters' chagrin. Fleshman says that may not be a bad thing.

“We see so many patients who want to go back to their job, who want to resume their life the way that it was," she says. "For her, it probably is the very best thing to stay at it."

'The fight of our lifetime'

How long she can stay at it is anyone's guess. That's why both liberal and conservative interest groups are preparing for the inevitable.

"We’ve been literally planning for her retirement for many years now," says Carrie Severino, chief counsel for the conservative Judicial Crisis Network, which raised and spent millions of dollars to promote the Gorsuch and Kavanaugh nominations. "Our commitment is to always be ready, because you can’t predict when a vacancy will come."

For liberals, "this will be the fight of our lifetime," Baker says – both because of what Senate Republicans did in 2016 to block Obama's choice and because it could impact the Supreme Court for generations to come.

“There could not be a higher-stakes battle for our country were that vacancy to occur," Baker says. "There will be an enormous mobilization of people making their voices heard.”

If Ginsburg's health holds out, next year's presidential and Senate elections will decide whether Democrats or Republicans choose her successor. If the White House and Senate end up in opposite hands, a stalemate could result in an extended vacancy.

That's a risk liberals would gladly take.

"It seems like for more than a decade, Supreme Court observers have been trying to guess Ruth Bader Ginsburg’s last day as a justice. It's a hopeless effort," says Elizabeth Wydra, president of the liberal Constitutional Accountability Center. "She has an unmatched drive to do superlative work and an iron will to do whatever it takes to keep her body in shape to do it."