And Clarence Thomas sided with the 5-3 majority (Gorsuch did not participate; i assume because he never heard the oral arguments, but I haven’t seen the reason stated):

This decision by Justice Kagan is a major victory for voting rights plaintiffs, who have succeeded in turning the racial gerrymandering cause of action into an effective tool to go after partisan gerrymanders in Southern states. That Justice Kagan got Justice Thomas not only to vote this way but to sign onto the opinion (giving it precedential value) is a really big deal. Despite what is written in the text of the opinion, Justice Kagan, in a couple of footnotes (footnotes 1 and 7), attempts to solve the race or party problem by moving the Court much closer to the position of treating race and party as proxies for one another in the American South…

Justice Alito, in his partial dissent for himself, the Chief Justice, and Justice Kennedy, is incensed at the decision, seeing it as inconsistent with the Court’s earlier decision in Easley v. Cromartie. He begins his dissent with: “A precedent of this Court should not be treated like a disposable household item””say, a paper plate or napkin””to be used once and then tossed in the trash. But that is what the Court does today …

I haven’t read the decision, nor am I especially familiar with the details of the case. But the fact that Justice Thomas sided with the liberal majority is highly unusual and makes me think the majority might have a point. On the other hand, party is most definitely not an automatic proxy for race, party is an entity in and of itself and more than enough motive for redistricting. It’s hard to see how any party—in the South or elsewhere in the US—could avoid racial disparities in districts drawn strictly along party lines.

The sort of reasoning of the SCOTUS majority in this case reminds me somewhat of the mind-reading that was part of the recent liberal decisions on Trump’s EO and his supposedly discriminatory motive for it. The fact that Republicans in the South tend to be more white, and Democrats more black, is a given. And I haven’t seen anything that addresses a question I have, which is whether this reasoning would work in the opposite direction if Democrats did it to favor the Democratic Party (and black voters) in their districts. I don’t like gerrymandering in general, by the way, but it’s legal and has long been used by whatever party is in power at the time of the districting.

The author of the piece at the link, Rick Hasen (who is an expert in election law), has this to say about the decision in the suit:

The harm in the racial gerrymandering cases is not vote dilution (which is separately considered under the Voting Rights Act and Constitution). The harm has been conceived of as an expressive one of sending the message that voters have been separated on the basis of race without adequate justification. It is a theory J. O’Connor invented in the 1993 Shaw v. Reno case. Liberals used to hate the theory, till this decade, when they started using the theory to attack Republican gerrymanders that Republican legislatures justified as compelled by the Voting Rights Act…

The controversy comes from the analysis of District 12. That district raises the question whether race or party predominated in redistricting. This is a particularly difficult question in the American South, because of “conjoined polarization,” race and party overlap to a great extent, so the question of which predominates is somewhat nonsensical. I make that case extensively in a forthcoming essay, Race or Party, Party as Race, or Party All the Time: Three Uneasy Approaches to Conjoined Polarization in Redistricting and Voting Cases.

It seems nonsensical to me as well, and rather pernicious. According to Hasen:

Holy cow this is a big deal. It means that race and party are not really discrete categories and that discriminating on the basis of party in places of conjoined polarization is equivalent, at least sometimes, to making race the predominant factor in redistricting. This will lead to many more successful racial gerrymandering cases in the American South and elsewhere, and allow these cases to substitute for (so far unsuccessful) partisan gerrymandering claims involving some of these districts. (Why Justice Thomas went along with all of this is a mystery to me. He joined in the opinion, and his separate opinion expresses no disagreement with these footnotes.)

More here:

Alito in his dissent argued that the redrawn lines “are readily explained by political considerations.”

The state formed new lines to comply with the lower court’s ruling, but this also faces a lawsuit that a federal court will hear in June. The groups Common Cause and the League of Women Voters of North Carolina filed the lawsuit, which questions “the breadth to which lawmakers can draw districts for partisan advantage.”

That pending case seems to involve more general questions about politics, not race.