Sen. Elizabeth Warren (D-MA) has called for court-packing in the wake of Justice Stephen Breyer’s retirement from the Supreme Court.

In a tweet on Thursday, Warren extolled Joe Biden for his pledge to nominate the first black woman to the highest court in the land while pressing him to go even further. She tweeted:

Justice Breyer has an extraordinary record of public service. I’m very happy that President Biden will fill this seat by naming the first Black woman to the Supreme Court. And we ought to #ExpandTheCourt to give her at least four more new colleagues & rebalance this institution.

Court-packing entails adding more justices to the Supreme Court in order to shift the balance of power toward the nominating party. Currently, the court has six justices appointed by Republicans and three appointed by Democrats. If implemented, court-packing would destroy an independent judiciary as president after president appoints however many justices they desire to get an ideological outcome. It has been a hardcore progressive cause ever since former President Trump began shifting the balance of the court, starting with Justice Kavanaugh and accelerating into overdrive when Justice Barrett replaced the late Ruth Bader Ginsburg. Ironically, neither Ginsburg nor Breyer supported the idea and condemned it at every turn.

In April of last year, reports surfaced that Senate and House Democrats were working on legislation that would add four new justices to the U.S. Supreme Courtm even after Justice Breyer said that court-packing would erode any and all trust in the judiciary.

“If the public sees judges as ‘politicians in robes,’ its confidence in the courts, and in the rule of law itself, can only diminish, diminishing the court’s power, including its power to act as a ‘check’ on the other branches,” Breyer said in a speech to Harvard Law, later adding:

The court’s decision in the 2000 presidential election case, Bush v. Gore, is often referred to as an example of its favoritism of conservative causes. But the court did not hear or decide cases that affected the political disagreements arising out of the 2020 Trump v. Biden election. It did uphold the constitutionality of Obamacare, the health care program favored by liberals.

Speaking with NPR in 2019, Ginsburg criticized past attempts to pack the Supreme Court, such as when President Franklin Roosevelt attempted to do so in the 1930s.

“Nine seems to be a good number,” the justice said. “It’s been that way for a long time. I think it was a bad idea when President Franklin Roosevelt tried to pack the Court.”

Even if President Biden and the Democrats were enthusiastically committed to packing the Supreme Court, they would undoubtedly have an uphill battle from the likes of moderate Sens. Kyrsten Sinema (D-AZ) and Joe Manchin (D-WV). In fact, shortly after the 2020 election, Manchin pledged he would not vote to end the filibuster or pack the court, a promise he has so far kept.

“With packing the courts, I’m not voting for that,” Manchin told CNN.