Throughout the Democratic primary process, former vice president Joe Biden resisted the idea of adding more Supreme Court seats to block a conservative judicial majority if Democrats wrestle back control of the White House and both chambers of Congress.
It would just become a vicious cycle, Mr Biden has said, with each party swelling the ranks of the court to suit its partisan interests each time it takes power in Washington.
“We add three justices — next time around, we lose control, they add three justices,” he said at a debate last year when asked about his views on “court-packing,” the colloquial term for diluting the ideological makeup of the Supreme Court by expanding the bench.
But with Donald Trump and the Senate Republican majority poised to seat a third justice in less than four years after the death last week of Justice Ruth Bader Ginsburg, several Democrats have issued calls for Mr Biden to reconsider the manoeuvre.
The US has expanded — and shrunk — the Supreme Court before, and it’s time to do it again, they argue.
Here’s how court-packing works, a nuts-and-bolts history on the makeup of the Supreme Court, and why it has been such a hot topic this election cycle.
What is court-packing and how do you do it?
Court-packing is the process of adding more judges to an existing court, whether that be the US Supreme Court, which seats nine justices, one of the 13 federal appeals court circuits, which vary in size, or any other court.
The US Constitution does not specify how many federal judges there must be, including on the Supreme Court. Congress and the president can adjust the number by passing and signing a simple bill, just like any other federal law.
While the Constitution only requires simple majorities in both chambers to pass a bill, Senate norms for debating legislation over the last several decades have made that a much more difficult endeavor in practice.
Since 1975, Senate rules have required 60 senators to vote to “invoke cloture” — that is, end debate — on any piece of legislation and bring it up for a vote. That, in effect, has meant a bill needs 60 senators to support it for it to pass — not the simple 51-vote majority outlined in the US Constitution.
Unless the Senate scraps the 60-vote rule to terminate debate on legislation, which Mr Biden has indicated he could potentially support, a simple Democratic majority in both chambers after the 2020 elections could not pass a court-packing bill.
How are judges appointed and confirmed?
To fill a seat on the federal judiciary, including the Supreme Court, the president first selects a nominee.
Technically, any US citizen can be nominated for the federal bench, regardless of their legal background, age or where they were born. The Constitution does not specify any requirements.
Informally, however, a nominee undergoes intense vetting by both the White House and the Senate Judiciary Committee, which then holds a public hearing — or a series of hearings, in the case of most Supreme Court justices — to question the nominee.
The Judiciary Committee then votes on whether to advance the nominee out of committee for official action on the Senate floor.
Once on the Senate floor, the majority leader sets time for official debate on the nomination. For decades, until 2013, Senate rules required 60 votes to end debate on all judicial nominations.
But that year, Democratic Senate Majority Leader Harry Reid ditched the 60-vote rule in favour of the Constitution’s simple majority clause for all federal judicial appointments except Supreme Court justices.
Four years later, during the 2017 confirmation process for Supreme Court Justice Neil Gorsuch, Republican Senate Majority Leader Mitch McConnell scrapped the 60-vote rule for nominees for the high court.
Once the chamber has voted to end debate, senators move onto the final confirmation vote, which requires a simple majority.
Have there always been nine Supreme Court justice?
No. The First Congress in 1989 established a Supreme Court with six justices: one chief justice and five associate justices.
It expanded to seven justices in 1807; nine in 1837; and 10 in 1863.
In 1869, the Circuit Judges Act returned the Supreme Court to nine seats.
While the number of Supreme Court justices has remained fixed at nine since 1869, the government has added hundreds of seats to the federal bench since 1950, more than doubling the number of appellate court judges and tripling the number of district court judges in that time to keep up with population growth and more criminal and civil cases.
What has Joe Biden said recently about court-packing?
Since Justice Ginsburg died last Thursday, Mr Biden has been more circumspect about his feelings on court-packing.
“It’s a legitimate question, but let me tell you why I’m not going to answer that question,” he told a reporter when asked point-blank whether he would seek to add more Supreme Court justices.
“It will shift the focus. That’s what [Trump] wants. He never wants to talk about the issue at hand, and he always tries to change the subject. Let’s say I answer that question, then the whole debate’s gonna be about what Biden said or didn’t say. … The discussion shoul dbe about why he is moving in a direction that’s totally inconsistent with what the founders wanted,” Mr Biden said, indicating his belief that the Senate should not seat a Supreme Court justice so close to an election in which thousands of Americans have already cast early ballots.
What has Donald Trump said about court-packing?
The Supreme Court already has five justices who are generally considered conservative, although Chief Justice John Roberts, a George W Bush appointee, has voted with the liberal bloc on several key occasions in recent years.
With the death of Justice Ginsburg, whom Mr Trump has called an “amazing lady,” only three Democratic president-appointed justices remain: Elena Kagan and Sonia Sotomayor (Obama) and Stephen Breyer (Bill Clinton).
Mr Trump has warned that if Mr Biden becomes president he will “pack the Supreme Court with far left radicals who will unilaterally transform American society far beyond recognition.”
Democrats will “mutilate the law, disfigure the Constitution and impose a socialist vision from the bench that could never pass at the ballot box,” Mr Trump has said.