GEOFF BENNETT: The U.S. Supreme Court today heard arguments in a key racial gerrymandering case out of South Carolina.

The state redrew their congressional map, moving thousands of Black voters out of a competitive congressional district, shoring it up as reliably Republican and diluting the Black vote.

The outcome could determine the balance of power in Congress.

For more on today's court proceedings, we're joined by "NewsHour" Supreme Court analyst Marcia Coyle.

Marcia, it's good to see you.

MARCIA COYLE: Good to see you, Geoff.

GEOFF BENNETT: So we know that two lower courts agreed that there was a clear racial gerrymander in this case, but at least a handful of the conservative justices on the Supreme Court today appeared to cast doubt on that.

Tell us more.

MARCIA COYLE: OK. First, let me say that a racial gerrymander is when a district has been drawn with race as the predominant motive or factor.

That's unconstitutional under the 14th Amendment equal protection guarantee.

During the arguments today, the chief justice and Justice Alito both seemed to be somewhat skeptical that the challengers here, the South Carolina Conference of the NAACP, had carried its burden of what they call disentangling race from politics.

Politics was what the state legislature claimed was its motive when it drew District 1 in South Carolina.

The chief justice said, for example, that there was no direct evidence that race was used.

There were no kind of bizarrely shaped lines around the district, which is often a tipoff.

He said that all it is, all they had was circumstantial evidence.

And if the court were to accept that, he said that could be a huge change or expansion of the court's voting rights jurisprudence.

That was really the strongest comment, I think, that was made about the challengers' evidence and their arguments today.

But there was pushback.

Justices Kagan and Justice Sotomayor felt that the circumstantial evidence, one, was very strong, and that was all that was needed under the court's voting rights jurisprudence.

They said that the lower court had found that what other right -- what other reason could there be, other than race, when you see the legislature move 30,000 Black voters out of the district into another district in an attempt, basically, to keep a 17 percent of Black voting age population in District 1?

So there was pushback there, and yet I think what all the justices seem to agree today on is that this is a very, very difficult case, trying to separate out whether race was the predominant motive or whether partisanship was the predominant motive.

And, Geoff, as you know, partisan gerrymanders are not unconstitutional.

GEOFF BENNETT: And the impact here is, of course, huge.

Our team spoke with South Carolina public radio reporter Thelisha Eaddy, who explained what this means for local voters in South Carolina.

THELISHA EADDY, South Carolina Public Radio: Some voices will not be heard during the next congressional, state and other local elections.

So for the Black residents who are now living in this diluted or cracked First Congressional District, issues that matter to them will be hard to hear, or hard to get representation for those issues moving forward.

And then for those voters who have been packed into the Sixth Congressional District, issues that matter to them or their larger community, these coastal issues, those voices or those issues may have a hard time being heard because they are now lumped in with residents who live almost 100 miles away.

GEOFF BENNETT: So that's the potential impact on folks in South Carolina.

What are the national implications, Marcia?

MARCIA COYLE: There are a number of redistricting battles going on right now throughout the country.

They're not all racial gerrymander claims.

Some of them are under the Voting Rights Act.

And yet you know that courts and litigators will be watching what the Supreme Court says today.

And what it does say today could very well have an impact on, for example, the U.S. House elections and control of the U.S. House in 2024.

So that's a very significant impact.

Also, the challengers claim that, if they don't succeed here, that state legislatures will be able to use politics or partisanship as a proxy for race and shield their plans from challenges.

On the other side, the legislature claims that, if the court rules against them, it's going to draw courts into very difficult battles trying to find the difference here, whether it is race or politics.

GEOFF BENNETT: "NewsHour" Supreme Court analyst Marcia Coyle, thanks so much for your time.

MARCIA COYLE: Thank you, Geoff.