I keep having this recurring thought that the existing Supreme Court could simply refuse to seat extraneous justices (i.e., >9) due to budget and space restrictions. Given that the Supreme Court is an independent Constitutional body, co-equal with the Executive and Legislative branches, I’m not sure Congress can actually legislate new Justice positions, or that the President can actually force them to increase their number simply by nominating extra Justices. What would the Congress say if the Supreme Court told them they had to double the number of Representatives or Senators? Or what would the President say if the Supreme Court told him he had to give the Vice President more to do, and make him a co-president rather than a subordinate? Yet this is precisely what the Democrats think Congress and/or the President can do to the Supreme Court.
That being said, the original reason for there being seven Justices on the original Supreme Court was that each of them was the Chief Judge of one of the seven circuits — and they were theoretically required to ride their circuit when the Supreme Court wasn’t in session. So if we went back to the Framers’ vision, there should be 13 justices today. (12 regional circuit courts plus the Federal Circuit.)
I could see increasing the number of Supreme Court Justices to 13, but then making them each directly responsible for one of the circuits (i.e., as per the original plan, each Justice is Chief Judge of their assigned circuit) and making them literally sit on that circuit when it is in session. Can you imagine — a circuit court of appeals getting ready to issue a stupid ruling, when the Chief Judge of the Circuit comes down and says, calmly, “You know that opinion will never fly when we hear it in the Supreme Court. And that’s not an ‘if’ — it’s a ‘when’.”
It would also make sense under such a system to appoint successor Justices based on geography; for instance, if the Justice who serves as Chief Judge for the Ninth Circuit dies or retires, the President is obligated to choose a nominee from the geographical area served by the Ninth Circuit. Which I suspect would help cut back on the number of Yale and Harvard graduates serving on the Court, and would also create balance rather than perpetuate the “clubby” nature of the existing Supreme Court.
The overriding need, however, is for the country to stop looking at the Supreme Court to protect us from our stupid mistakes in choosing incompetent legislators. The justices have made it clear for years that they do not want to serve as a “super-legislature” set in place to fix vague and contradictory law made in Congress. Either Scalia or Alito (I think) said at one point not many years ago that they would prefer the American people simply sent better people to Congress who would write unambiguous law that didn’t leave 90% of its interpretation to the permanent bureaucracy. Or something along those lines. The problem is, the Democrats can’t get what they want in Congress, so they’re pushing for the Supreme Court to act as that “super-legislature” in order to interpret the law to say what they want it to say. But thus has it ever been; it’s no historical secret that FDR wanted to pack the Court for precisely that reason.
ADDENDUM, 14 Oct 2020: As I have mulled this thing over, I also keep coming back to the idea that the number of justices on the Court shouldn’t be within the purview of either the President or the Congress. The number of justices on the court should be determined by the Court itself, as a function of workload. The original Judiciary Act set the number at six in 1789. In 1807, Congress increased the number to seven (probably to prevent ties). In 1837 it was raised to 9, and in 1863 it was raised to 10. The Judicial Circuits Act of 1866 was passed by the Radical Republicans to lower the number of justices to 7, and deny Andrew Johnson any nominees to the Court. In 1869, with Johnson gone and U.S. Grant firmly ensconced at 1600 Pennsylvania Avenue, Congress raised the number back to 9, and it has been 9 ever since, despite the attempted depredations threatened by the traitor FDR. I would think at this point that a 151-year tradition is set in stare decisis stone, and any changes to the makeup of the Supreme Court ought to be at the request of the Court, not instituted by whim of the President or the Congress…but then, I’m an originalist and think we need to be paying more attention to following the Constitution rather than packing the Court to change its Constitutional function into a sort of mini-House of Lords. I would therefore propose an Amendment to the Constitution whereby the number of Supreme Court Justices would be set permanently at 9, and could be increased (or decreased) only by the Court itself.
The bottom line is that you don’t see Congress thinking its numbers ought to be increased — no, they’re traditionally jealous of their privileges, and would argue the current numbers are historical precedent, and can only be changed if states are added to the Union (and they wouldn’t even do that when Alaska and Hawaii were admitted back in the ’50s). Whereas one of the few suggestions Jonah Goldberg has made over the years that are actually worth serious consideration is the one he made back in ’09 to increase the House to around 5,000 members. And even he admitted that would be a hard sell in Congress.