The Supreme Court building in Washington on March 11. (Mark Tenally/AP)

Sen. Marco Rubio (R-Fla.) declared earlier this week his intention to introduce a constitutional amendment to limit the number of Supreme Court justices to nine. That’s a great move — one that will help entrench judicial independence. But since Democrats are unlikely to approve such a measure, he should be open to some amendments that could entice them to support his core principle: creating a constitutional limit on the number of justices, even if it means raising the number of appointments on the bench.

Rubio’s move comes as Democrats are increasingly endorsing the idea of adding an indeterminate number of seats to the court to counteract Republican appointments (currently five of the court’s nine members). From a narrow partisan viewpoint, one can understand why they would want to do this: The court installed so many of the policies that Democrats value via constitutional interpretations rather than legislation. A determined Republican majority could, in theory, overturn or narrowly interpret many of these cases, dealing serious blows to the progressive agenda.

The Democratic proposals should be rejected, nevertheless, because they would effectively destroy the court’s ability to independently interpret the Constitution. Once the unwritten norm of keeping the court’s number at nine is breached, a political party would be tempted to simply pack the court any time it makes a sweeping ruling with which the party disagrees. Justices would surely temper their judgments should that become the norm, swaying with the political winds to maintain their relative importance. And the court would become even more of a political football than it is now, to the detriment of the rule of law.

Rubio’s core proposal, therefore, is sound. But in the current political environment, it is highly unlikely to pass, as it would lock in the Republican majority. Since the two oldest justices, Stephen G. Breyer and Ruth Bader Ginsburg, are both Democratic appointees, a permanent cap of nine at this stage would more likely increase the Republican majority in the short term, especially if President Trump wins reelection. Even if he does not, it is likely that Republicans will retain their Senate majority through at least 2022, and the decision in 2016 by Senate Majority Leader Mitch McConnell (R-Ky.) to not hold hearings on President Barack Obama’s nominee, Merrick Garland, suggests that even a Democratic president could not successfully place his or her nominee on the bench if Breyer or Ginsburg were to step down while Republicans control the Senate.

These considerations mean that Rubio should be open to compromise proposals if it means getting Democratic votes for a firm cap on the number of justices. Such a compromise could involve a constitutional requirement for the entire Senate to hold a floor vote on any presidential nomination: no more Garlands. It could mean increasing the number of justices to 11 or 13, and staggering those increases so that the new seats are filled after the 2020 and/or 2024 elections. It would give the Democrats a chance to “catch up” if their candidate wins, while also providing for additional Republican appointments if Trump or another Republican is elected.

Either or both provisions would address a deeply held Democratic concern while installing the principle of judicial independence firmly in our Constitution. Democrats may not want to go along with these measures, but then that is something they would have to defend in the court of public opinion during the 2020 campaign. If Republicans are willing to meet them halfway and they still say no, Republicans could reasonably argue that Democrats appear more concerned with political control of the courts and Constitution than redressing legitimate grievances.

It could be that our politics are so toxic that they no longer permit serious give-and-take in addressing our challenges. That would be a shame, especially when our challenge is preserving the rule of law and judicial independence in the face of serious political disagreements over judicial rulings. The court has often ruled in ways we find odious (for example, the Dred Scott decision), but the proper way to address odious rulings is to overturn them through statute or constitutional amendment, not by subjecting the court itself to direct political control through court packing.

Rubio deserves applause for his decision to introduce his amendment. We can only hope that the rest of the members of Congress take his challenge seriously and work together to place the judicial independence on a firm constitutional footing.

Read more:

Megan McArdle: Some things should never be resurrected. Court-packing is one of them.

Marc A. Thiessen: Trump isn’t the biggest threat to the Constitution. Democrats are.

Jennifer Rubin: Why court-packing is a really bad idea

Paul Waldman: Why court-packing suddenly looks appealing to Democrats