Last week’s constitutional amendment vote in the House of Representatives tells us something about the state of Congress today. It also tells us something about the state of Congress in the future.

The constitutional amendment the House considered—known informally as the “Keep Nine” amendment—would write the current structure of the Supreme Court into the Constitution: It would fix the number of Court seats at nine, “consisting of one chief justice and eight associate justices.” Practically, the amendment would change nothing, given that the Court has been composed of nine justices for over 150 years.

The vote for the amendment failed; it received only a simple majority in the House, while the passage of a constitutional amendment requires a two-thirds vote. If we look at this vote as a way to predict the future, it is much more useful: Every House Republican voted for it, and nearly every House Democrat voted against it. (Rep. Don Davis of North Carolina was the only Democrat to vote with Republicans on the amendment.)

Of course, not every legislator who voted against the amendment can be expected to try to expand the Court in the future. As Rule 156 of the Securities and Exchange Commission reminds us, past performance is no guarantee of future results. But the almost entirely partisan verdict the amendment received suggests that a great many House Democrats would welcome expansion. This marks a significant shift in elite opinion: As Josh Orton, head of the pro-expansion group Demand Justice, said, “What was once a fairly dramatic and fringe idea has now become mainstream.” 

My view is that Supreme Court expansion is quite dangerous. Suppose that, in a few years, Kamala Harris’ proposal last month to expand the Court to 13 justices is realized—perhaps under a future Democratic congressional majority. What is to stop a succeeding Republican majority from additional, retaliatory Supreme Court expansion in the middle of the 2030s? The answer to this question surely cannot be that a second expansion would fly in the face of established, time-honored norms; the first expansion discarded those.

A few weeks ago, Rep. Jim Clyburn (D‑SC) appeared on Meet the Press to explain his position on expansion: “Thirteen is a pretty good number. A baker’s dozen would be a good number to have on the court.” It is easy to imagine, a decade from now, some smirking Republican legislator appearing on Meet the Press to make an argument of the same quality. It could be something along the lines of: “As we all know, thirteen is unlucky. But twenty-five—five squared—is a big, beautiful number that sounds good to me!” Ultimately, there is no magic number of Court seats—thirteen, twenty-five, or whatever—that is worth the almost inevitable tit-for-tat cycle that any such expansion would create.

A serious, principled argument for Supreme Court expansion is difficult to find—although there is no shortage of cosmetic justifications. Kamala Harris has argued that we need 13 justices because there are 13 federal circuits, but circuit riding ended more than a century ago. That argument is weak. Except for administrative attention to the occasional emergency appeal, the duties of the circuit justices are essentially ceremonial. 

Some legislators, such as Sen. Sheldon Whitehouse (D‑RI), have argued that expansion is necessary because some justices are corrupt. But this argument misfires: Putting aside questionable factual claims about particular instances of corruption, the proper remedy for corrupt justices is removal through impeachment. Expanding the number of Supreme Court seats is an unserious way to address alleged corruption; at best, expansion would dilute corruption rather than resolve it. 

Finally, Rep. Jerry Nadler (D‑NY) has argued that the Court is simply overloaded with work and therefore needs the help that additional justices could provide; this is a hard argument to make, given that the Court has chosen to cut its merits caseload in half. Forty years ago, the Court heard roughly 150 argued cases per term, but it now hears about 60 cases yearly—so it is hard to understand why the Court’s workload is unprecedentedly heavy. Indeed, President Franklin D. Roosevelt (FDR) made the heavy-workload argument nearly a century ago to justify his own court-packing scheme; it was unpersuasive then, and the Court’s relatively tiny merits docket makes it even more unpersuasive now. (In contrast, the problem of docket overload at lower judicial levels is a real and serious one; it has been true for a long time that, in lower courts, the US needs more federal judges.)

Other arguments for Court expansion lack the patina of political neutrality: For instance, some have argued that the Senate has used its advice and consent power to create asymmetrical and unfair confirmation results, culminating in decisions that are genetically illegitimate because they lack popular support. Ultimately, such arguments appear to be driven by a dislike for the current Court’s work product. But a principled opinion about Supreme Court expansion needs to rest on something more than a distaste for what the Court produces. Calling for expansion on the basis of perceived historical unfairness will never provide a decisive or ultimate resolution of any related controversy. In this context, expansion would be something like the latest episode of hostilities in a war between Hatfields and McCoys, in which ancient grievances are regularly stoked but never resolved.

The vote on the Keep Nine amendment tells us something important about elite political opinion and its sharp partisan divides. I am grateful that popular opinion is considerably more nuanced. Large bipartisan majorities of Americans favor significant Court reforms (e.g., term limits for justices, binding ethics rules), but this is not true for Supreme Court expansion. There are parallels here: FDR was ultimately responsible for a huge number of structural changes to American government, but his administration’s popularity failed to transfer to his advocacy for court-packing. 

With any luck, congressional elites who are handed the option to expand the Court will pay attention to popular opinion on this question. My guess is that, once the public is exposed to more sustained discussion about this question, the relatively weak popular support for Court expansion is likely to shrink even further. I suppose the Supreme Court is something like a snowball—it can get bigger as it rolls downhill—and I hope Congress is wise enough not to push it in that direction.