AMNA NAWAZ: The U.S. Supreme Court today heard arguments in a landmark election case looking at whether former President Donald Trump's actions on January 6 should disqualify him from appearing on the Republican primary ballot in Colorado.

For over two hours, the justices scrutinized an obscure provision in the 14th Amendment at the center of this case.

That provision says that former elected officials should be barred from holding office if guilty of insurrection.

Former President Trump weighed in after the arguments concluded.

DONALD TRUMP, Former President of the United States (R) and Current U.S. Presidential Candidate: You're leading in the country by a lot.

And can you take the person leading everywhere and say, hey, we're not going to let you run?

I think that's pretty tough to do, but I'm leaving it up to the Supreme Court.

AMNA NAWAZ: Our own William Brangham and Supreme Court analyst Marcia Coyle were both at the court today and join me here now.

It's great to see you both.

WILLIAM BRANGHAM: Hi.

MARCIA COYLE: Good to see you.

AMNA NAWAZ: So, William, we reported on this last night, but just remind us, what is the main argument in Colorado's case here?

WILLIAM BRANGHAM: A group of Republican voters in Colorado watched January 6 happen, and they said that was an insurrection and Donald Trump was responsible for it.

And so they petitioned their state to say that, under Section 3 of the 14th Amendment, which is the so-called Insurrection Clause, that he should be disqualified from running and from becoming president again.

Section 3, if you remember, basically says that, if you're elected to office and you swear an oath to the Constitution, but then you commit an insurrection, you're ineligible to be in office again unless two-thirds of the Congress wipes that stain away from you.

And so they argued this to their -- went all the way up to the Colorado state Supreme Court.

A split decision sided with them.

That was the case that was being argued today.

AMNA NAWAZ: And, Marcia, in listening to this, which I have to say is so cool to be able to do, but it didn't sound like it broke along partisan lines, right?

Justices on both sides had questions and issues.

One major question was about the power of states in enforcing that Insurrection Clause, Section 3.

Chief Justice John Roberts actually said this: JOHN ROBERTS, Chief Justice of the U.S. Supreme Court: In very quick order, I would expect, although my predictions have never been correct, I would expect that a goodly number of states will say, whoever the Democratic candidate is, you're off the ballot, and others, for the Republican candidate, you're off the ballot, and it'll come down to just a handful of states that are going to decide the presidential election.

That's a pretty daunting consequence.

AMNA NAWAZ: Marcia, what exactly are his concerns here?

MARCIA COYLE: Well, I think, as you mentioned, the key issue that the justices did appear to be most interested in -- and that's across the bench -- was the -- whether the states have a role to enforce Section 3 against non-state candidates like a president.

And Mr. Trump's attorney argues that they have no role at all, absent congressional legislation giving them authorization.

The Colorado lawyer argued that the states have broad power under Article 2, the Electors Clause, in order to run elections, and that includes enforcing qualifications for the ballot.

So the chief justice took it a step further, and he asked the hypothetical, assuming states do have the power to do this, is this what's going to start happening?

You're going to have different states with different standards, different definitions of, for example, insurrection and different rules for holding a trial on that, and it's just going to be -- become very political?

There's going to be retaliation.

If they throw a Republican off the ballot, a state that is upset about that might throw a Democrat off the ballot.

And that's when I felt the arguments also started to turn quite a bit against Colorado and in favor of Mr. Trump's arguments.

So, that's what the chief justice was basically saying, and it was picked up by other justices voicing similar concerns.

WILLIAM BRANGHAM: I mean, to that point, it is what you were saying, Amna, about how this really did split along -- not split along ideological lines.

Another issue that did come up was this question of whether Section 3 actually applies to the presidency, because, in the clause -- in the section itself, it lists all the different offices that could be disqualified if you commit an insurrection.

President is not mentioned in that list.

Everyone sort of assumed they meant it, but Ketanji Brown Jackson picked that up today.

Let's listen to what she had to say about that.

KETANJI BROWN JACKSON, U.S. Supreme Court Associate Justice: But then why didn't they put the word president in the very enumerated list in Section 3?

The thing that really is troubling to me is, I totally understand your argument, but they were listing people that were barred, and president is not there.

JASON MURRAY, Attorney Representing Colorado Voters: This came up in the debates in Congress over Section 3, where Reverdy Johnson said, why haven't you included president and vice president in the language?

And Senator Moore responds, we have.

Look at the language, any office under the United States.

And... KETANJI BROWN JACKSON: Yes, but doesn't that at least suggest ambiguity?

And this sort of ties into Justice Kavanaugh's point.

In other words, we had a person right there at the time saying what I'm saying.

The language here doesn't seem to include president.

Why is that?

And so, if there's an ambiguity, why would we construe it to, as Justice Kavanaugh pointed out, against democracy?

AMNA NAWAZ: It's fascinating how much of this goes around just the language at play here.

But, William, did they ever address that central point you mentioned there, that January 6 was an insurrection, that President Trump was responsible in some way for it?

WILLIAM BRANGHAM: Yes, you would think that would have been a central line of questioning, but it really wasn't today.

I mean, the point about was this an insurrection or not or even Donald Trump's role on January 6 barely came up.

The lawyer from Colorado, Jason Murray, kept trying to insert that into his answers.

But the justices, again, they get to choose what parts of these laws they need and rulings they want to talk about.

This is not -- they're not relitigating the entire case.

But it was surprising how little that came up.

Marcia and I both felt that way.

I do want to play this one bit where Justice Kavanaugh was questioning Jason Murray, the lawyer representing Colorado, about this, where he was arguing, to the point that Marcia was making, that if you allow Colorado to basically dictate who sits on the presidential ballot, that that, in and of itself, is antidemocratic.

Listen to this exchange.

BRETT KAVANAUGH, U.S. Supreme Court Associate Justice: In trying to figure out what Section 3 means, and to the extent it's elusive language or vague language, what about the idea that we should think about democracy, think about the right of the people to elect candidates of their choice, of letting the people decide?

Because your position has the effect of disenfranchising voters to a significant degree.

JASON MURRAY: This case illustrates the danger of refusing to apply Section 3 as written, because the reason we're here is that President Trump tried to disenfranchise 80 million Americans who voted against him, and the Constitution doesn't require that he be given another chance.

WILLIAM BRANGHAM: So that's about as close as they got to putting this case before the justices about whether January 6 was an insurrection.

AMNA NAWAZ: Marcia, meanwhile, this is all playing out as the public watches it, right?

There were calls, we should mention, for Justice Thomas to recuse himself because of his wife's involvement in January 6.

He did not.

There's been scrutiny of the credibility of the court.

And now they have an enormous decision before them about whether or not a former president should be on a primary ballot.

When are they going to make this decision?

And, also, they have to figure out whether or not to take up the case regarding former president's immunity case as well.

MARCIA COYLE: That's right.

Yes, in fact, well, as far as the case today that was argued, I expect that they may move fairly quickly.

I mean, they moved quickly to schedule briefing and arguments in this case.

I think they're very aware that there are primary election deadlines approaching, ballot questions.

And the question of President -- former President Trump's immunity is something he has to actually take the next step, since he lost in the lower court, no immunity.

He's got to appeal to the Supreme Court by Monday in order to stop the lower court's ruling from moving forward to the trial judge, and the trial actually taking place.

So we will see more of that.

And I think the court is very aware of all of this, as well as how it's viewed as an institution and what its ruling can be.

In a lot of ways, the case today is a lose-lose.

Whoever wins -- or whoever loses, there's going to be criticism of the court and probably political criticism.

So, it's tough.

But that's what they get paid to do.

(LAUGHTER) AMNA NAWAZ: Marcia Coyle, William Brangham, thank you so much.

MARCIA COYLE: Thank you.

WILLIAM BRANGHAM: Thank you.