Standing at just five-foot-one, Ruth Bader Ginsburg may be diminutive in stature, but the US Supreme Court Justice has become a feminist hero and pop-culture icon.

She has been immortalised in books and movies.

Her image is emblazoned onto coffee mugs and t-shirts, along with her unlikely rap-inspired nickname: Notorious RBG.

In recent months though, it's her ailing health that has dominated headlines and loomed large over America's legal landscape.

What's wrong with her health?

The 86-year-old has broken three ribs in a fall, had cancerous growths removed from her lungs and just this week, was treated in hospital for chills and a fever.

She was released days later with a Supreme Court spokeswoman confirming, "she is home and doing well."

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"Hang in there, Justice Ginsburg. We need you like never before," said one fan on Twitter.

"Everyone pray for RBG," demanded another.

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She has already survived three bouts of cancer and each time her latest health scare becomes public, it sends her supporters into a panic (and Washington into collective cardiac arrest).

Late-night hosts Stephen Colbert and Jimmy Kimmel have given voice to this anxiety, promising to help Justice Ginsburg get back on her feet.

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Unveiling the "Ruth Bader Gins-bubble" (a giant plastic bubble with a Ginsburg look-a-like inside) Kimmel declared the Justice needs to be protected "at all costs".

Colbert likened her to a precious jewelled egg.

"Forget the black robe. She should be dressed in bubble wrap and carried down the hallway like a Faberge Egg!" he said.

Why do the Democrats want to keep her alive?

This concern is not just for her welfare, but for the future direction of the highest court in the country (akin to Australia's High Court).

Appointed by President Bill Clinton in 1993, Ginsburg is a leading progressive who has become known for her incisive questions and fiery dissents, particularly in cases where she believes the rights of women or minorities have been overlooked.

In 2014, the court ruled that companies did not have to abide by federal laws and provide contraceptive coverage as part of their employees' health insurance.

Justice Bader wrote a 35-page dissenting report concluding: "the Court, I fear, has ventured into a minefield".

If she leaves the court, President Donald Trump will get to nominate her replacement.

Five Supreme Court justices were chosen by conservative presidents, and the remaining four were chosen by more progressive presidents. ( Supplied: Fred Schilling )

That would be his third Supreme Court Justice after already having appointed Brett Kavanaugh and Neil Gorsuch (both of whom were considered controversial, partisan picks).

This would cement a 6-3 conservative majority on the nine-person bench (the justices serve for life) and could profoundly change the court's direction for decades to come.

So, in a sense, Justice Ginsburg's supporters see her as a progressive bulwark against that.

The justices hear fewer than 100 cases a year but their rulings set precedents that affect everything from reproductive rights and same-sex marriage to the executive power of the President.

Occasionally, they can revisit an issue and change their own precedent, which is what anti-abortion activists are hoping will come to pass in the event of another conservative appointment.

Justice Ginsburg has previously expressed reservations about whether the landmark 1973 Roe v Wade ruling (protecting a woman's right to abortion) will be preserved.

Ruth Bader Ginsburg has spoken out in support of legal decisions which give women the choice to abort a pregnancy. ( Reuters: Joshua Roberts )

The National Rifle Association and gun activists are keenly watching the composition of the nine-person bench too, hoping for an expansion of the Second Amendment right to bear arms.

Next week, the Supreme Court will hear its biggest guns case in more than a decade when it is asked to decide on New York's "draconian restrictions" on the possession and transport of handguns.

What about the Republicans?

Republican pundits say Ruth Bader Ginsburg's occasional naps during public events are evidence she is getting too old for the job. ( Reuters: Jason Reed )

According to political pundits, if there were two issues that energise Trump's base, it's the right to own a gun and the right to life.

That is why Mr Trump makes such a big deal out of his judicial appointments because these rights can be defined, protected and eroded by the Supreme Court.

According to reports, the White House has been reaching out to political allies and conservative activist groups preparing for Justice Ginsburg's possible death or departure from the bench.

And whomever Trump chooses is almost guaranteed to be appointed, after the Republican-controlled Senate lowered the threshold in 2016 to confirm a Supreme Court justice.

What's the likelihood she leaves her seat soon?

As things stand, the 86-year-old is going nowhere.

At 86, Ruth Bader Ginsburg is the oldest judge sitting on the US Supreme Court, and among Democrats, the most popular. ( ABC News: Jonathan Ernst )

Hers is a job for life and she has repeatedly said she will remain in the role "as long as I'm healthy and mentally agile".

"My senior colleague, Justice John Paul Stevens, stepped down when he was 90, so I think I have a way to go," she has said in the past.

The self-described flaming feminist litigator has spent her long life ending discrimination, breaking down barriers for women and flourishing in the face of adversity.

When she was treated for pancreatic cancer during the Obama Administration, she faced calls to stand down so that a Democratic President could choose a progressive replacement.

"There was a senator, I think it was after the pancreatic cancer, who announced with great glee that I was going to be dead within six months," Ginsburg recalled earlier this year.

"That senator, whose name I've forgotten, is now himself dead, and I am very much alive."