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 RubioThe Memo: 'Whistleblower' furor gains steam Liberal super PAC launches browser extension replacing 'Mitch McConnell' with 'Moscow Mitch' Trump faces difficult balancing act with reelection campaign 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 CramerPrimary challenges show potential cracks in Trump's GOP Castro, Steyer join pledge opposing the Keystone XL pipeline EPA proposes rolling back states' authority over pipeline projects MORE (N.D.), Marsha BlackburnMarsha BlackburnTaylor Swift 'obsessed' with politics, says she's cautious about celebrity support backfiring for Democrats The evolution of Taylor Swift's political activism Kellyanne Conway responds to Taylor Swift criticism by invoking pop star's lyrics MORE (Tenn.), Todd YoungTodd Christopher YoungSenators pressure Trump to help end humanitarian crisis in Kashmir Congress set for chaotic fall sprint Overnight Defense: Senate fails to override Trump veto on Saudi arms sales | Two US troops killed in Afghanistan | Senators tee up nominations, budget deal ahead of recess MORE (Ind.), Cindy Hyde-Smith (Miss.), John HoevenJohn Henry HoevenBottom Line Poll: McConnell is most unpopular senator McConnell ups pressure on White House to get a budget deal MORE (N.D.), Mike LeeMichael (Mike) Shumway LeeZuckerberg woos Washington critics during visit Zuckerberg to meet with lawmakers to discuss 'future internet regulation' Hillicon Valley: Election security looms over funding talks | Antitrust enforcers in turf war | Facebook details new oversight board | Apple fights EU tax bill MORE (Utah), Ben SasseBenjamin (Ben) Eric SasseManufacturing group leads coalition to urge Congress to reauthorize Ex-Im Bank The Hill's Morning Report - Trump ousts Bolton; GOP exhales after win in NC Trump endorses Sasse in 2020 race MORE (Neb.), Mitt RomneyWillard (Mitt) Mitt RomneyBolton replacement inherits tough challenges — including Trump Bipartisan group of senators urges FDA to pull most e-cigarettes immediately Trump judicial picks face rare GOP opposition MORE (Utah), Mike CrapoMichael (Mike) Dean CrapoBipartisan housing finance reform on the road less taken 2020 Democrats raise alarm about China's intellectual property theft Trump faces tough path to Fannie Mae, Freddie Mac overhaul MORE (Idaho), and Shelley Moore CapitoShelley Wellons Moore CapitoThis week: House jump-starts effort to prevent shutdown Congress set to ignore Trump's wall request in stopgap measure America is in desperate need of infrastructure investment: Senate highway bill a step in the right direction 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 WarrenWarren overtakes Biden in Iowa for first time: poll Warren avoids attacks while building momentum Sanders unveils plan to eliminate Americans' medical debt MORE (D-Mass.) and Kamala HarrisKamala Devi HarrisWarren overtakes Biden in Iowa for first time: poll Iowa GOP swipes at 2020 Democrats' meat positions as candidates attend annual Steak Fry Warren avoids attacks while building momentum 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.

Sen. Kirsten GillibrandKirsten GillibrandBooker aide sounds alarm about campaign's funding O'Rourke gun confiscation talk alarms Democrats Gillibrand relaunches PAC to elect women MORE (D-N.Y.) told "Pod Save America" that the idea was “interesting” and she would “need to think more about it.”
 
Supporters argue that President TrumpDonald John TrumpAlaska Republican Party cancels 2020 primary Ukrainian official denies Trump pressured president Trump goes after New York Times, Washington Post: 'They have gone totally CRAZY!!!!' 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.