There is a debate on the left over whether the Democrats should try to "pack" the Supreme Court the next time they get the opportunity to do so. Support for court-packing within the Democratic Party is growing. But many liberals remain opposed to the idea, warning that it is likely to do more harm than good. Over the last few days, two leading left of center constitutional law scholars have written insightful pieces highlighting some of the dangers of court-packing: Noah Feldman (Harvard) and Neil Siegel (Duke). Both works make good points.

One of the most important is the way they address the standard liberal rationale for resorting to court-packing: the idea that it is a justifiable response to the Republican-controlled Senate's refusal to hold hearings or a vote on President Obama's Supreme Court nominee, Merrick Garland in 2016. Both point out that court-packing would not be a proportionate response, but a major escalation in the conflict. Here's Siegel on that issue:

I agree that Senate Republicans behaved very badly by, among other things, refusing even to consider President Obama's nomination of Chief Judge Merrick Garland, who was supremely qualified, experienced, and ideologically moderate. But there are difficult line-drawing problems here. For example, if the full Senate had voted Garland down on the merits as insufficiently conservative (a deeply unfortunate but not norm-defying outcome, in my view), we would presumably have the same Court we have now, and yet Court-packing would not seem a justifiable response. In addition, and moving from the question of whether Court-packing is justified in response to flagrant norm violations by the Republicans to whether Court-packing would be wise, the Democrats can at some point retaliate in tit-for-tat fashion for the mistreatment of Garland by refusing to consider a Republican Supreme Court nominee. (And, by the way, I would not limit such retaliation to the last year of a Republican President's term, which is a distinction without a relevant difference.) Proportionality is important to prevent conflict escalation and so to avoid fueling a race to the bottom.

And Feldman:

The proportionate response would be for Democrats to refuse to confirm a Republican president's nominee when they control the Senate. Democrats would then effectively be saying that Republicans have changed the background rules of confirmation. It would follow, that we might get an incredible shrinking Supreme Court, with nominees added only when the president and the Senate majority come from the same party. There are reasons to think that's a bad idea; but in any case it would be a state of affairs that followed logically from the Republican decision to block Garland. A proportionate response is a tit-for-tat strategy: Whatever you do to me, I do back to you. Such a strategy can help reestablish equilibrium when it is in danger of being permanently broken. In contrast, packing the court would be a disproportionate response to the Garland affair. Instead of doing what the Republicans did, Democrats would be raising the stakes by transforming the balance of the court in one fell swoop, rather than one justice is a time. That in turn would invite Republicans to retaliate by doing the same thing. Instead of a shrinking Supreme Court, the result could be a vastly expanded Supreme Court, one that gets new members each time the president and Senate come from the same party. That would be unsustainable. Not only could the court grow to an unmanageable size; its rulings could zigzag from one ideological extreme to the other. A zigzagging court, deciding every case on ideological grounds, is the antithesis of the rule of law. Decisions must produce at least some degree of settled expectations for them to contribute to governance by law rather than by judicial fiat.

Siegel is also right to point out that the GOP's refusal to hold hearings on Garland differed only in degree from voting him down and doing the same to any other Obama nominee the Republicans considered too liberal. I would add that it was also little different from what then-Senator Barack Obama and many other Democrats unsuccessfully tried to do in 2006 with the nomination of Samuel Alito: prevent a vote from occurring by using the filibuster (a move Obama later said he regretted). A filibuster prevents nominees from coming to a vote no less than the GOP's 2016 strategy did. Republicans also argued (plausibly, in my view) that their 2016 strategy was a proportionate response to Democrats' use of similar tactics against lower-court nominees, and statements suggesting they would do the same thing if a GOP president had the opportunity to name a justice late in his term.

In fairness, Obama's 2006 strategy did permit hearings on Alito's nomination, even as he sought to block a vote. Majority Leader Mitch McConnell's 2016 tactics did not even allow hearings. But I suspect Democrats would have been only slightly less angry if McConnell had permitted hearings on Garland, but blocked a vote.

None of this necessarily proves that the GOP's refusal to vote on Garland was justified. But it does indicate that any norm against blocking nominees was far less clear than that against court-packing, which both parties had previously adhered to for many decades.

Feldman and Siegel also emphasize the institutional damage that court-packing would do, which goes far beyond anything that has happened in the last several decades of judicial nomination wars. Here, I think they actually underrate the risk somewhat. The problem is not just that the Court would "zigzag" (Feldman) or see its legitimacy damaged (Siegel), but that the institution of judicial review would be severely undermined by the rendering the Supreme Court subservient to whichever party manages to control the presidency and Congress simultaneously. It is no accident that court-packing is a standard tool of authoritarian populists seeking to undermine liberal democracy, recently used in such countries as Hungary, Turkey, and Venezuela. Would-be authoritarians know that independent courts are an obstacle to their illiberal measures, and that court-packing is an effective way to neuter them.

The problem is unlikely to be limited to the Supreme Court, as similar strategies could be used to pack the lower courts, as well. Indeed, the current round of debates over court-packing arguably began in 2017 when prominent conservative legal scholar Steve Calabresi and his coauthor Shams Hirji proposed a plan for Republicans to do just that. I opposed that plan for much the same reasons as I now object to Democratic court-packing proposals. But if the Supreme Court gets packed, both parties are likely to revive versions of the Calabresi-Hirji plan to do the same for other federal courts.

Rejecting court-packing does not mean that Democrats (or anyone else) should necessarily reject all proposals for reforming the Supreme Court. I have previously pointed out that such reform proposals as limiting justices to 18-year terms do not pose the same sorts of risks. Similarly, it would be reasonable for Democrats to seek some concession in exchange for supporting a constitutional amendment limiting the size of the Court, and thereby permanently eliminating the risk of packing. I suggested one possible deal of that sort here. Current GOP proposals for an anti-court packing amendment are unlikely to succeed without some such agreement.

I don't agree with every point that Siegel and Feldman make. For example, unlike Siegel, I am skeptical that using the threat of court-packing is a relatively safe idea even if those who make the threat have no intention of actually carrying it out. Like court-packing itself, the threat of doing it is a game both parties can play, if it turns out to be effective. Over time, effective threats can also undermine judicial independence. Moreover, it is difficult to make such a threat effectively without actually being prepared to carry it out, should the justices refuse to give in to the president who makes it. A credible threat would require the president to mobilize his or her party's base in favor of court-packing, thereby creating strong expectations that the threat would be carried out if the justices continue to make rulings the president's party finds highly objectionable.

Regardless of such quibbles, Feldman and Siegel have made valuable contributions to the court-packing debate. Anyone interested in the issue should make sure to read them!

UPDATE: I should perhaps note that Feldman and Siegel are not the only liberal critics of court-packing. I noted several others here, including Laurence Tribe and former Obama White House Counsel Bob Bauer.