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When will Supreme Court Justices Ruth Bader Ginsburg and Stephen Breyer retire?

It's a question that has surfaced as the Supreme Court term has come to an end in recent years.

READ: ABC News' Supreme Court Coverage

But anticipation about the future plans of Ginsburg and Breyer has taken on a new sense of urgency in some liberal legal circles, with Democrats locked in a bitter struggle with Republicans to keep control of the Senate in the fall midterm elections. The discussion is a delicate one, out of deference to the justices, but several lawyers say it's quietly echoing from the White House to Congress and beyond.

"The only way that Ruth Bader Ginsburg can be sure that someone with her views and values replaces her is to step down at the end of this term," said Erwin Chemerinsky, the dean of the UC-Irvine Law School, who called on the justices to retire in a Los Angeles Times editorial in March.

Ginsburg, 81, and Breyer, 75, are two of the leading liberal voices on the court, and also among the oldest. Ginsburg, a two-time cancer survivor, has endured the loudest calls to step down.

Should either justice retire in the final two years of President Obama's term, Democrats would find it difficult to replace to progressive judges with like-minded successors if Republicans control the Senate. Even if Democrats keep their narrow majority, confirming a Supreme Court justice takes 60 votes and becomes increasingly more difficult at the end of a presidency.

"Can you just imagine, if we had a vacancy on the court, how long it would take to get a justice approved, with the opposition and obstruction of the Republican Senate," House Minority Leader Nancy Pelosi said Wednesday at her weekly press conference on Capitol Hill.

If Ginsburg and Breyer remain on the court through Obama's term, they run the risk of being replaced by more conservative justices in 2016 if Republicans win back the White House.

While the political stakes are tangible for liberals - two less progressives on the bench would give conservatives a 7-2 majority - many Democrats are unwilling to weigh into the thorny question of how long Supreme Court justices should serve.

"They're both functioning, good judges. I think this is up to them," said Sen. Dianne Feinstein, D-Calif., who sits on the Senate Judiciary Committee. "I have great respect for them both."

House Minority Leader Nancy Pelosi , also a Democrat, said she has "every confidence" in the justice's ability on the court and called arguments for Ginsburg's retirement "inappropriate."

Former Justice John Paul Stevens told ABC News that justices should "have an interest in who's going to fill your shoes," but Ginsburg has said the party of the next president won't factor into her decision.

WATCH: John Paul Stevens: Okay To Consider Politics In Retirement Decision

Regardless, Ginsburg and the rest of the court still have a session to finish. The court has not yet delivered a ruling on the much-anticipated Hobby Lobby case, which is expected by Monday.