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 RubioSenate Republicans tested on Trump support after Mueller Cuban negotiator says Trump's efforts to destabilize Cuba's government will fail Freedom to Compete Act would benefit many American workers 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 ToomeyOvernight 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 Top GOP candidate drops out of Ohio Senate race MORE (Pa.), Kevin CramerKevin John CramerCain says he 'won't run away from criticism' in push for Fed seat Cain says he won't back down, wants to be nominated to Fed Conservatives urge Trump to stick with Moore for Fed MORE (N.D.), Marsha BlackburnMarsha BlackburnConservative groups defend tech from GOP crackdown Lawmakers weigh challenges in fighting robocalls Senators show deep skepticism on Space Force proposal MORE (Tenn.), Todd YoungTodd Christopher YoungGOP senators divided on Trump trade pushback Menendez, Rubio lead Senate effort to regulate Venezuelan sanctions Senate GOP proposes constitutional amendment to keep Supreme Court at 9 seats MORE (Ind.), Cindy Hyde-Smith (Miss.), John HoevenJohn Henry HoevenOvernight Energy: Bipartisan Senate group seeks more funding for carbon capture technology | Dems want documents on Interior pick's lobbying work | Officials push to produce more electric vehicle batteries in US Officials, automakers aim to produce more electric vehicle batteries in US: report FCC claims on broadband access under scrutiny MORE (N.D.), Mike LeeMichael (Mike) Shumway LeeDems sound alarm over top DOJ nominee Restore Pell Grant eligibility to people in prison Former Democratic aide pleads guilty to doxing GOP senators attending Kavanaugh hearing MORE (Utah), Ben SasseBenjamin (Ben) Eric SasseSenate needs to stand up to Trump's Nixonian view of the Fed GOP senators divided on Trump trade pushback The Hill's 12:30 Report: Assange faces US charges after dramatic arrest MORE (Neb.), Mitt RomneyWillard (Mitt) Mitt RomneyGiuliani: 'Nothing wrong' with campaign taking information from Russians Earth Day founder's daughter: Most Republican leaders believe in climate change in private Senate Republicans tested on Trump support after Mueller MORE (Utah), Mike CrapoMichael (Mike) Dean CrapoGraham says he's 'not interested' in Mueller testifying Senate needs to stand up to Trump's Nixonian view of the Fed Senate bill seeks to bring freedom back to banking MORE (Idaho), and Shelley Moore CapitoShelley Wellons Moore Capito20 Dems demand no more money for ICE agents, Trump wall We can accelerate a cure for Alzheimer's Gillibrand, Grassley reintroduce campus sexual assault bill 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 WarrenTim Ryan doesn't back impeachment proceedings against Trump Schiff: Democrats 'may' take up impeachment proceedings Trump claims Democrats' plans to probe admin will cost them 'big time' in 2020 MORE (D-Mass.) and Kamala HarrisKamala Devi HarrisCory Booker has a problem in 2020: Kamala Harris Booker to supporter who wanted him to punch Trump: 'Black guys like us, we don't get away with that' Tulsi Gabbard fundraises off 4/20: 'Appalls me' that feds consider marijuana illegal 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 TrumpThorny part of obstruction of justice is proving intent, that's a job for Congress Obama condemns attacks in Sri Lanka as 'an attack on humanity' Schiff rips Conway's 'display of alternative facts' on Russian election interference 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.