Republican Rep. Mark Green of Tennessee said Tuesday he is introducing a constitutional amendment to limit the number of justices on the Supreme Court to nine, after several Democratic presidential candidates have expressed support for expanding the number of justices to 15.

"This Thursday, I will be introducing a constitutional amendment that would limit the number of Supreme Court justices to 9 — the number of seats since 1869," Greene said on Twitter. "The Supreme Court must remain a fair and impartial branch of government not beholden to party ... Schemes to pack the court are dangerous to the Founders' vision of an independent judiciary that serves as a check on both the Executive and Legislative branches of government."

The Constitution doesn't specify the number of justices on the Supreme Court, leaving its composition up to Congress. The number of justices changed several times in early U.S. history before reaching its current total of nine.

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Sen. Marco Rubio, R-Fla., also tweeted he would introduce an amendment to keep the number of justices at nine.

"We must prevent further destabilization of essential institutions. Court packing is quickly becoming a litmus test for 2020 Democratic candidates. Therefore I will be introducing a constitutional amendment to keep the number of seats on #SCOTUS at 9," Rubio wrote.

Democratic presidential candidates like Pete Buttigieg and Beto O'Rourke have argued the Supreme Court is already too partisan. They have hinted at supporting a reform that would give Republicans and Democrats five justices each, with an additional five justices chosen by the first 10.

"This central objective that is to prevent the Supreme Court from continuing on this trajectory to become basically ruined by being a nakedly political institution," Buttigieg said in an interview with "Pod Save America." "This idea of adding justices is one way to do it."

Sens. Kamala Harris, Elizabeth Warren and Kirsten Gillibrand also told Politico they would consider supporting an expansion of the Supreme Court if elected president.

"It's not just about expansion, it's about depoliticizing the Supreme Court," Warren said.

Republicans like Green and Rubio think adding justices would make the court even more partisan, but Democrats argue the GOP tarnished the court's impartiality when Senate Majority Leader Mitch McConnell refused to allow a vote on Merrick Garland, who was nominated by President Obama in 2016, leaving a Supreme Court seat open for roughly a year.