The U.S. Supreme Court on Thursday made it far more difficult to challenge state redistricting plans as unconstitutional racial gerrymanders. By a vote of 6-to-3, along ideological lines, the court upheld a redistricting map drawn by the South Carolina legislature, a map that a lower court found had resulted in “the bleaching of African American voters” from a district.

At issue in the case was the way the Republican-dominated South Carolina legislature drew new lines for congressional districts after the 2020 Census. The problem it faced was how to equalize the number of voters in each district. Specifically, the 1st Congressional District had 88,000 too many voters, and the adjoining 6th District, represented by the state’s only Black member of Congress, had lost almost the same number of voters. In the end, the legislature moved some 200,000 Black voters into new districts and chopped up Charleston County, stripping from CD1 much of the city of Charleston, and ending the city’s 120-year history as the anchor for the district.

Republicans denied exiling Black voters, maintaining that they were simply seeking to transform a marginal Republican district into a safe district for the GOP.

The South Carolina NAACP challenged the redistricting in court, and a three-judge federal district court, after a nine-day hearing, ruled that new map was an unconstitutional racial gerrymander. But on Thursday the Supreme Court did something highly unusual. It didn’t just overrule the lower court. It said the facts found by that court were “clearly erroneous” and the court majority then went on to themselves re-examine the facts, reaching diametrically different conclusions.

Writing for the court’s six conservatives, Justice Samuel Alito said that the South Carolina map was a partisan gerrymander, which is legal, not a racial gerrymander, which would be illegal under the Constitution. In short, he said that the map achieved the GOP’s political goals, nothing more.

“Justice Alito has been the one who has really been the leader in weakening protections for minority voters," says UCLA election law expert Richard Hasen.

NYU law professor Richard Pildes contends that the problem is bigger than the intricacies of this and other cases, mainly in the South, where Black and white voters are highly polarized, and their voting patterns strongly correlate with race. Yet under the court’s 2019 decision, partisan gerrymandering is perfectly legal, while racial gerrymandering is not.

“It can be very hard in these cases to sort out whether people are being moved as part of a political gerrymander or part of a racial gerrymander,” Pildes says.

Highlighting that dilemma, the court’s conservative majority imposed some stringent new limits on racial gerrymandering claims. One is that courts must assume the good faith of legislatures, even though redistricting is avowedly partisan. And two, the court raised the bar for the kinds of evidence that plaintiffs must present to prevail.

Dissenting from Thursday’s ruling were the court’s three liberal justices.

“In every way, the majority today stacks the deck against the challengers,” wrote Justice Elena Kagan in dissent. “It does not matter that the challengers offered extensive evidence” that the redistricting “was the product of racial sorting. It does not matter that the state, by way of response, offered little more than strained and awkward denials."

“When racial classifications in voting are the issue, the majority says every doubt must be resolved in favor of the state,” Kagan observed. “And so this odious practice of sorting citizens by race,” will continue, she added. “In the electoral sphere especially, where ugly patterns of pervasive racial discrimination have so long governed,” she concluded, “we should demand better—of ourselves, of our political representatives, and most of all, of this court.”