GEOFF BENNETT: A Georgia appeals court has disqualified the top prosecutor overseeing an election interference case against president-elect Donald Trump and his allies, a decision that could upend the case.

Fulton County district attorney Fani Willis was disqualified because she had a romantic relationship with an attorney she hired to help run the investigation.

The decision overturns a lower court ruling earlier this year that said Willis could continue in the role.

Our William Brangham has been following the legal cases against Mr. Trump and joins us now.

So, William, what was the appeals court's argument in removing Fani Willis from this case?

WILLIAM BRANGHAM: Their argument -- and I should say, this came as a bit of a surprise, because the presiding judge, as you said, Scott McAfee, who is a conservative appointed by Republican Governor Brian Kemp, had criticized Willis' relationship and said it created this appearance of impropriety, but said, if you get rid of the man you're having a relationship with, you can stay on the case.

She did that.

This appeals court comes in and, while agreeing that this was really just about an appearance of impropriety, they said that this case was so rare and so unusual that it -- quote -- "that disqualification was mandated."

Now, they have been criticized a fair amount for this ruling.

It was a 2-1 decision, but that's the ruling.

And she's off the case.

GEOFF BENNETT: The underlying case, though, hasn't been dismissed.

Could it be prosecuted by someone else potentially?

WILLIAM BRANGHAM: Potentially.

Fani Willis' office is appealing to the Georgia Supreme Court to overthrow this so she could get back in the driver's seat.

Unclear if that's going to happen.

If she loses that, then there's this Republican-led Council of Prosecutors in Georgia, and they will be the ones to decide, drop the case, continue the case, and then assign a new prosecutor to that.

Unclear if that's going to happen or not.

Hanging over all of this, though, is also this Department of Justice Office of Legal Counsel policy, which says that no sitting president can be prosecuted.

Now, Department of Justice, that's usually thought of as covering just federal cases, not state and local, but the belief among many legal experts is, is that state and local prosecutors would have to honor this as well.

And so the other cases against Mark Meadows and Rudy Giuliani, other people involved in this case, could go forward, but there's just nobody really believes that a judge in Georgia would allow a case to go against Donald Trump when he's back in the White House.

So... GEOFF BENNETT: So, looking at the landscape of all of the cases that existed, I guess I use the past tense, existed... WILLIAM BRANGHAM: That's the right tense.

GEOFF BENNETT: That's right, yes.

I mean, which ones remain?

Any of them?

WILLIAM BRANGHAM: No.

The two federal cases against Donald Trump, we know Jack Smith has wound those down.

The other one was dismissed, this case in Georgia really in limbo.

The only one that still has some legal maneuvers going on is the Stormy Daniels case, 34 felony convictions against Donald Trump in New York City.

The judge just threw out Trump's attempt to say, hey, the Supreme Court just granted me immunity.

I ought to be able to throw this case out.

He said, no, no, no, not so fast.

But he has postponed sentencing, perhaps not until Donald Trump is out of the White House.

GEOFF BENNETT: William Brangham, our thanks to you, as always.

WILLIAM BRANGHAM: Thanks, Geoff.