I have heard from various seasoned Supreme Court practitioners and former clerks that you can typically only lose ground in oral arguments, not gain it. I.e. Oral argument that can be carefully crafted and gussied up in the briefing can fall apart under scrutiny at argument. But you'll rarely if ever be able to persuade the Court at oral argument about a point that wasn't persuasive in dozens of pages of briefing.

My favorite example of this is in Citizens United, where the Government's attorney, in response to a question from Justice Alito, conceded that the Government's interpretation of the First Amendment would allow it to ban political books close to an election. See pp. 26-27: https://www.supremecourt.gov/oral_arguments/argument_transcr...

Regarding citizens united, is that really something that only came to light in oral arguments? Isn't this a criticism that the opposition would raise in their own briefing package?

Was the relevance simply the admission that the government didn't have an answer to the criticism?

You’re correct that the significance was that the government’s admission at argument revealed that it did not have a robust principle for distinguishing between the political movie at issue in that case with books.

I don’t recall the details, but I’m sure it came up in the opposition’s briefs. But in a brief you can paper over a thin argument to an extent. You can accuse the opposition of invoking a slippery slope, spend a lot of words making subtle distinctions, etc. It’s certainly fair to say that parties’ briefs often overstate the gravity of the consequences one way or another. So upon reading the briefs, the response might seem quite plausible. But when you’re forced to give a succinct answer to a direct question at oral argument, that kind of evasion falls apart and you’re forced to fully own the implications of your position.

I would say that the oral argument has zero impact whatsoever.

Which could point to the Supreme Court being a relic of its time and so partisan and ideologically driven that the entire court is closer to a ceremonial performance than a specific aspect like orals.

Or, in the alternative, it would point to the Supreme Court receiving tens of thousands of words of briefing on the issues prior to argument, supplemented by internal bench memos from their law clerks (some of the brightest young lawyers in the country).