(CNN) — President Joe Biden promised Black voters Wednesday that he would appoint progressives to the US Supreme Court if elected to a second term, suggesting he expects vacancies on the high court over the next four years.

“The next president, they’re going to be able to appoint a couple justices, and I’ll be damned — if in fact we’re able to change some of the justices when they retire and put in really progressive judges like we’ve always had, tell me that won’t change your life,” he said during a campaign rally in Philadelphia.

It was as explicit a warning as Biden could offer about the stakes of the upcoming election, and a clear reminder that some of the nine justices have entered their seventies.

Clarence Thomas is 75 and Samuel Alito is 74; both are conservative and appointed by Republican presidents. Sonia Sotomayor, a liberal who was nominated by President Barack Obama, turns 70 next month.

Retirements of any or all of those justices could provide a key opportunity for either Biden, who has named one justice to the Supreme Court, or his Republican rival Donald Trump, who named three during his four-year term.

The ideological makeup of the court has emerged as one of the defining facets of American political power. The current conservative majority — made possible by Trump’s three appointments — overturned in 2022 the nationwide right to abortion enshrined in Roe v. Wade, opening a major front in this year’s election. Gun ownership rights, voter protections and regulatory issues have also come before the panel.

Justices rarely signal their intentions to retire before announcing them through the court. And presidents have traditionally tread carefully when speaking publicly about the prospect of retirement-age justices stepping down.

At the start of his term, Biden made clear to aides there would be no efforts to pressure Justice Stephen Breyer, then age 83, into retirement, even though many Democrats were eager for the political opening such a vacancy would provide.

The hands-off approach was rooted in respect for the justice, whose confirmation Biden oversaw as chairman of the Senate Judiciary Committee, and out of fear an overt pressure campaign might backfire. Liberal groups not affiliated with the White House were more explicit in calls for Breyer to retire.

Breyer announced his retirement in January 2022, allowing Biden to fulfill a campaign pledge to nominate a Black woman to the court, Ketanji Brown Jackson.

Other presidents have adopted a somewhat similar approach. Trump, through his White House counsel Don McGahn, did not make explicit calls for Justice Anthony Kennedy to retire early in his term. Instead, he consulted the justice on lower court nominations as a way to cultivate a degree of comfort with the process.

Obama is said to have danced around the retirement question with Ruth Bader Ginsburg at a lunch in 2013. Then the court’s oldest member, she did not retire during Obama’s term. She died while still on the bench in 2020, and Trump quickly nominated conservative Amy Coney Barrett to replace her.

As he attempts a return to the White House, Trump has made his own nominees to the court a selling point, and promised additional conservative selections if he were to win.

“Many presidents never get the opportunity to appoint a Supreme Court justice. I had three. They are gold,” he said at a 2023 speech at the Moms for Liberty summit. “Maybe we’ll get three or four more. Can you imagine?”

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