Senate Republicans are moving to keep the Supreme Court at nine justices as a growing number of Democratic 2020 contenders have expressed an openness to expanding it. 
 
Roughly a dozen Republican senators introduced the resolution on Monday that would keep the Supreme Court at nine justices. 
 
"The Democrats' court-packing proposal represents the latest shortsighted effort to undermine America's confidence in our institutions and our democracy," Sen. Marco RubioMarco Antonio RubioDes Moines Register endorses Elizabeth Warren as Democratic presidential nominee Commerce Department withdraws Huawei rule after Pentagon pushback: reports  Veronica Escobar to give Spanish-language response to Trump State of the Union address MORE (R-Fla.), who spearheaded the resolution, said in a statement.
 
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He added that he was introducing the constitutional amendment "to prevent the delegitimizing of the Supreme Court."
 
GOP Sens. Pat ToomeyPatrick (Pat) Joseph ToomeyNSA improperly collected US phone records in October, new documents show Overnight Defense: Pick for South Korean envoy splits with Trump on nuclear threat | McCain blasts move to suspend Korean military exercises | White House defends Trump salute of North Korean general WH backpedals on Trump's 'due process' remark on guns MORE (Pa.), Kevin CramerKevin John CramerThe Hill's Morning Report - House prosecutes Trump as 'lawless,' 'corrupt' Collins walks impeachment tightrope Senate Republicans muscle through rules for Trump trial MORE (N.D.), Marsha BlackburnMarsha BlackburnTaylor Swift on publicist's Trump warning before political post: 'F--- that, I don't care' GOP cries boredom in attack on impeachment case Marsha Blackburn shares what book she's reading during Trump Senate trial MORE (Tenn.), Todd YoungTodd Christopher YoungRestlessness, light rule-breaking and milk spotted on Senate floor as impeachment trial rolls on Impeachment trial forces senators to scrap fundraisers Iran resolution supporters fear impeachment will put it on back burner MORE (Ind.), Cindy Hyde-Smith (Miss.), John HoevenJohn Henry HoevenBottom Line The Hill's Morning Report — Schiff: Clear evidence of a quid pro quo Trump steps up GOP charm offensive as impeachment looms MORE (N.D.), Mike LeeMichael (Mike) Shumway LeeThe self-fulfilling Iran prophecy No patriotic poll bump for Trump, but Soleimani strike may still help him politically Senators are politicians, not jurors — they should act like it MORE (Utah), Ben SasseBenjamin (Ben) Eric SasseTrump legal team offers brisk opening defense of president Commerce Department withdraws Huawei rule after Pentagon pushback: reports  The Hill's 12:30 Report: Dems to present case on abuse of power on trial's third day MORE (Neb.), Mitt RomneyWillard (Mitt) Mitt RomneyKaine: GOP senators should 'at least' treat Trump trial with seriousness of traffic court Des Moines Register endorses Elizabeth Warren as Democratic presidential nominee Romney: 'It's very likely I'll be in favor of witnesses' in Trump impeachment trial MORE (Utah), Mike CrapoMichael (Mike) Dean CrapoSenators ask FDA to crack down on non-dairy milks, cheeses Drug price outrage threatens to be liability for GOP It's time for the Senate to advance cannabis banking reform MORE (Idaho), and Shelley Moore CapitoShelley Wellons Moore CapitoDemocrat Richard Ojeda announces Senate bid after dropping out of presidential race Spending bill to address miners' health care, pensions Manchin warns he'll slow-walk government funding bill until he gets deal on miners legislation MORE (W.Va) are cosponsoring the resolution. 
 
The Senate resolution would specify that the Supreme Court "shall be composed of not more than 9 justices." A similar resolution was introduced in the House late last week. 
 
Enacting a constitutional amendment would be an uphill battle, if not an impossible goal. The amendment would first need to win over two-thirds of both chambers of Congress, and then be ratified by three-fourths of the states.
 
But Rubio first announced last week that he would introduce the amendment after several Democratic White House contenders, including a handful that are Rubio's Senate colleagues, expressed an openness to expanding the Supreme Court or enacting other judicial reforms, including term limits. 
 
Both Sens. Elizabeth WarrenElizabeth Ann WarrenDes Moines Register endorses Elizabeth Warren as Democratic presidential nominee Sanders faces lingering questions about appeal to women voters Sunday shows preview: Lawmakers prepare for week two of impeachment trial MORE (D-Mass.) and Kamala HarrisKamala Devi HarrisHarris on 2020 endorsement: 'I am not thinking about it right now' Panel: Is Kamala Harris a hypocrite for mulling a Joe Biden endorsement? The Hill's Morning Report — Dems detail case to remove Trump for abuse of power MORE (D-Calif.) have said expanding, or "packing," the court should be an option on the table as part of a larger conversation among Democrats about the direction of the U.S. judicial system.

 
Supporters argue that President TrumpDonald John TrumpKaine: Obama called Trump a 'fascist' during 2016 campaign Kaine: GOP senators should 'at least' treat Trump trial with seriousness of traffic court Louise Linton, wife of Mnuchin, deletes Instagram post in support of Greta Thunberg MORE and congressional Republicans have been able to pack the courts with conservative judges, including two Supreme Court justices and dozens of appeals court nominees.

But Rubio countered in a Fox News op-ed last week that trying to expand the courts had become a "litmus test" for White House hopefuls and stemmed from an "ugly, winner-take-all rhetoric" among progressives.