As President Trump moves to nominate a candidate to fill the seat of Justice Ruth Bader Ginsburg, who died Friday, there are a growing number of Democrats threatening to implement a radical strategy and pack the Supreme Court if they take control of the White House and the Senate.

“If he holds a vote in 2020, we pack the court in 2021,” Rep. Joe Kennedy III, D-Mass., tweeted on Saturday. “It’s that simple.”

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“Mitch McConnell set the precedent. No Supreme Court vacancies filled in an election year. If he violates it, when Democrats control the Senate in the next Congress, we must abolish the filibuster and expand the Supreme Court,” Sen. Ed Markey, D-Mass., tweeted.

The idea of “packing” the court with extra justices -- attempted unsuccessfully by President Franklin Delano Roosevelt in 1937 to force through parts of his New Deal that were ruled unconstitutional by the high court -- has bubbled away on the fringes of the party for years.

But it began to seep into the mainstream after Republicans refused to hold hearings for Merrick Garland -- President Barack Obama’s 2016 pick to replace Justice Antonin Scalia -- because it was an election year.

Consequently the seat was held open until after the 2017 inauguration of President Trump, who nominated now-Justice Neil Gorsuch. Many Democrats saw the seat as “stolen” as a result.

The Garland controversy has been cited by Democrats again now that Republicans are moving to fill Ginsburg's seat in an election year. They say that because Republicans refused to fill a seat in 2016, they should decline to fill this one in 2020.

Republicans, however, have said that the precedent is when the Senate is controlled by an opposition party to the White House.

Other Democrats have said that Democrats should consider court packing if the confirmation is delayed and occurs during a lame-duck session after Nov. 3.

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“If Sen. McConnell and @SenateGOP were to force through a nominee during the lame-duck session -- before a new Senate and President can take office -- then the incoming Senate should immediately move to expand the Supreme Court,” House Judiciary Chairman Jerry Nadler wrote on Twitter.

“Filling the SCOTUS vacancy during a lame-duck session, after the American people have voted for new leadership, is undemocratic and a clear violation of the public trust in elected officials. Congress would have to act and expanding the court would be the right place to start,” the New York Democrat continued.

It is unclear if Democratic nominee Joe Biden will back those calls. A number of his primary opponents, including his now-running mate Kamala Harris, signaled their openness last year to expanding the number of judges on the court if they enter the White House.

Biden, however, said in 2019 he was not prepared to pack the court, “because we’ll live to rue that day.”

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It remains to be seen if his stance will change given Ginsburg’s death, and what appears to be a shifting mood in the party on the question.

Democratic congressional leaders, meanwhile, have not explicitly supported court packing, but have suggested they are open to radical strategies if Republicans fill the seat. Sen. Minority Leader Chuck Schumer, D-N.Y., said in a caucus call with Senate Democrats Saturday that "nothing is off the table" if Republicans move forward with confirming a justice immediately.

“Let me be clear: if Leader McConnell and Senate Republicans move forward with this, then nothing is off the table for next year. Nothing is off the table," he said, a source on the call told Fox News. He added that "Everything Americans value is at stake."

House Speaker Nancy Pelosi has not talked about court packing, on Sunday refused to rule out measures such as impeaching the president if he moves to fill the seat.

“We have our options. We have arrows in our quiver that I’m not about to discuss right now, but the fact is we have a big challenge in our country,” Pelosi said on ABC News’ “This Week. “This president has threatened to not even accept the results of the election.”

Schumer and Pelosi's comments brought rebuke from the White House.

“The Speaker threatened to impeach the President -- again -- for simply fulfilling his constitutional obligation," White House Deputy Press Secretary Brian Morgenstern told Fox News. "Numerous Democrats are threatening to pack the court and say things like ‘nothing is off the table.’ These are bizarre and dangerous power grabs by Democrats who will stop at nothing to erode the Constitution to enact their radical agenda."

Democrats who would expand the court would also have to acknowledge that they did not have the support from Ginsburg herself -- who warned against court packing last year.

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"Nine seems to be a good number. It's been that way for a long time," she told NPR. "I think it was a bad idea when President Franklin Roosevelt tried to pack the court."

"Well, if anything would make the court appear partisan, it would be that," she said. "One side saying, 'When we're in power, we're going to enlarge the number of judges, so we would have more people who will vote the way we want them to.'"

Fox News' Brooke Singman and Morgan Phillips contributed to this report.