AMNA NAWAZ: Now for more on the president's unusual trip down Pennsylvania Avenue to the Supreme Court today, I'm joined by our Liz Landers at the White House.

So, Liz, let's begin with this remarkable moment of the president sitting in essentially as his own executive order is on trial.

What do we know about what's behind his unprecedented attendance?

LIZ LANDERS: Amna, President Trump has been talking about birthright citizenship since he launched his bid for the presidency in 2015.

And this has become a signature policy for the second Trump administration, immigration policy, and, in particular, clamping down on both illegal, but also legal pathways for immigration in this country.

They have managed to stop a lot of those southern border encounters.

But also, at the same time, we have seen in the past few months in particular ICE and CBP agents rounding up people throughout different American cities and deporting them.

And also Americans have been caught up in some of those actions as well.

This birthright citizenship is just another example of how the Trump administration is clamping down on both these legal and illegal pathways towards citizenship.

AMNA NAWAZ: Meanwhile, Liz, I know you have been talking to a number of your Republican sources today.

What are they telling you about how they're looking at this case and what the political ramifications of this court's decision could be for them, especially coming up with the midterm elections?

LIZ LANDERS: Amna, I spoke with one Republican who's close to the White House and in particular close to the political shop here, and this person told me that obviously if the Supreme Court sided with the president and ruled that birthright citizenship is no longer the law of the land, then that would be a big win for the president going into the November elections and could fire up his base, who is motivated by this issue of immigration.

But this person also acknowledged that overall this doesn't poll well in general with the American public.

Most Americans do support birthright citizenship.

This source pointed me to a Quinnipiac poll that came out last December that said that 70 percent of voters thought that the Supreme Court should keep this 1898 ruling in place and just 24 percent called on the court to reverse it.

In that same poll, they looked at Trump's overall handling of immigration issues, saying that 44 percent approved, while 54 percent disapproved.

Today, we heard some reaction from the president as he left the courthouse.

He posted on TRUTH Social a falsehood about birthright citizenship, saying that the United States is the only country in the world to allow this.

Amna, that is not the case.

There are a number of countries, including our neighbors to the north and the south, Canada and Mexico, that allow birthright citizenship, in addition to Argentina, Brazil, Pakistan, Peru, Venezuela, and other places -- Amna.

AMNA NAWAZ: And, Liz, as you have been reporting the president also continues to lie about some other issues as well, including widespread fraud in mail-in voting.

Last night, he just signed a related executive order.

That one delegates more authority to federal agencies to oversee elections.

It's already being met with a lot of pushback from some secretaries of state.

But what exactly does that attempt to do?

LIZ LANDERS: I want to be clear, Amna, that everyone that I have spoken with, both election attorneys, secretaries of state and other election officials in the country, have said in the last 24 hours to me that they do not think that this executive order is legal and will not stand up in court.

However, what the president is trying to do in this executive order is two things.

First of all, it's ordering the Department of Homeland Security secretary to compile a state citizenship list using information like Social Security data, naturalization records and other immigration records to determine who is eligible to vote.

Secondly, it would also direct the U.S.

Postal Service to create mail ballot envelopes with a bar code.

That would be used to track ballots that are put in through the mail.

And the United States Postal Service would also have to provide each state with a list of enrolled voters who are eligible for absentee and mail ballots.

Regardless of what this says, though, Amna, the president does not have constitutional authority over elections.

That is left to the states.

And then Congress has a limited role in overseeing election administration.

One top election official for Pennsylvania, a key swing state, the Republican Al Schmidt, he put out a statement saying that he's going to continue to ensure that voting is -- quote -- "not impeded by needless barriers justified by phantom threats of ineligible voters casting ballots."

Amna, Maine Secretary of State Shenna Bellows told me -- or said in a statement that it was laughably unconstitutional and she is not going to obey this order.

AMNA NAWAZ: And, Liz, to be clear, this mail-in voting method, it's the same one the president himself has used, right?

LIZ LANDERS: He used this in an election that happened just last week, Amna, a special Florida election.

He, his wife, the first lady and their son Barron all cast mail-in ballots.

I asked the president about this last week, asking him why he cast a mail-in ballot if he's repeatedly saying that this is not a reliable way of voting.

He didn't answer that question directly, but just said that he used the mail-in ballot because he's the president of the United States, he's busy, and, basically, that was the easiest option for him to use -- Amna.

AMNA NAWAZ: That's our White House correspondent, Liz Landers, reporting tonight.

Liz, thank you.