WASHINGTON (AP) — The Supreme Court 's conservative majority on Thursday preserved a Republican-held South Carolina congressional district, rejecting a lower-court ruling that said the district discriminated against Black voters.

In dissent, liberal justices warned that the court was insulating states from claims of unconstitutional racial gerrymandering.

In a 6-3 decision, the court held that South Carolina's Republican-controlled legislature did nothing wrong during redistricting when it strengthened Rep. Nancy Mace's hold on the coastal district by moving 30,000 Democratic-leaning Black residents of Charleston out of the district.

"I'm very disturbed about the outcome. It's as if we don't matter. But we do matter and our voices deserve to be heard," said Taiwan Scott, a Black voter who sued over the redistricting.

But Mace, reacting to the decision, said, "It reaffirms everything everyone in South Carolina already knows, which is that the line wasn't based on race."

The case presented the court with the tricky issue of how to distinguish race from politics. The state argued that partisan politics, not race, and a population boom in coastal areas explain the congressional map. Moving voters based on their politics is OK, the Supreme Court has held.

A lower court had ordered South Carolina to redraw the district after it found that the state used race as a proxy for partisan affiliation in violation of the equal protection clause of the 14th Amendment to the Constitution.

Thursday's decision won't have a direct effect on the 2024 election. The lower court had previously ordered the state to use the challenged map in the November vote, which could help Republicans as they try to hold on to their narrow majority in the House of Representatives.

Justice Samuel Alito, writing for the court, criticized lower-court judges for their "misguided approach" that refused to presume that lawmakers acted in good faith and gave too much credit to the challengers.

Alito wrote that one weakness of the Black voters' case was that they did not produce an alternative map, which he called an "implicit concession" that they couldn't have drawn one. "The District Court's conclusions are clearly erroneous because it did not follow this basic logic," he wrote.

Justice Elena Kagan, writing for the three liberals, said her conservative colleagues ignored the work of the lower court that found the district had been gerrymandered by race.

"Perhaps most dispiriting," Kagan wrote, the court adopted "special rules to specially disadvantage suits to remedy race-based redistricting."

Richard Hasen, an election expert at the University of California at Los Angeles law school, agreed with Kagan, writing in a blog post that the decision "makes it easier for Republican states to engage in redistricting to help white Republicans maximize their political power."

Janai Nelson, president and director-counsel of the NAACP Legal Defense and Educational Fund, said in a statement, "The highest court in our land greenlit racial discrimination in South Carolina's redistricting process, denied Black voters the right to be free from the race-based sorting and sent a message that facts, process, and precedent will not protect the Black vote."

However, Sen. Thomas Alexander, the president of the South Carolina Senate, praised the ruling. "As I have said throughout this process, our plan was meticulously crafted to comply with statutory and constitutional requirements, and I was completely confident we would prevail," Alexander said.

The Supreme Court in 2019 ruled that partisan gerrymandering cases could be not be brought in federal courts. Justice Clarence Thomas, who was part of the conservative majority five years ago, wrote separately Thursday to say federal courts should similarly get out of the business of refereeing racial gerrymandering disputes.

"It is well past time for the Court to return these political issues where they belong—the political branches," Thomas wrote. No other justice signed on.

When Mace first won election in 2020, she edged Democratic incumbent Rep. Joe Cunningham by 1%, under 5,400 votes. In 2022, following redistricting driven by the 2020 census results, Mace won reelection by 14%. She is among eight Republicans who voted in October to oust Kevin McCarthy, R-Calif., as House speaker.

The case differed from one in Alabama in which the court ruled last year that Republican lawmakers diluted Black voters' political power under the landmark Voting Rights Act by drawing just one district with a majority Black population. The court's decision led to new maps in Alabama and Louisiana with a second district where Democratic-leaning Black voters comprise a substantial portion of the electorate.

In South Carolina, Black voters wouldn't have been as numerous in a redrawn district. But combined with a substantial set of Democratic-leaning white voters, Democrats might have been competitive in the reconfigured district.

The high court left open one part of the case about whether the map intentionally sought to dilute the votes of Black residents.

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Associated Press writers Ayanna Alexander and Farnoush Amiri contributed to this report.