The decision comes as the problem of gerrymandering has grown much worse, for two reasons. First, technological improvements have allowed line drawers to use sophisticated software and demographic analysis to create ever more effective gerrymanders. Even in wave elections, some of these gerrymanders will let a party preferred by a minority of voters capture a majority of seats. This is not theoretical. It has happened again and again.

Second, we are in an era of hyperpartisanship, when a politician pays no political consequences (and indeed gets rewarded) for publicly declaring a partisan purpose. Indeed, Rucho involved a Republican gerrymander of North Carolina’s 13 congressional districts, and David Lewis, one of the Republican legislative leaders, said in 2016 that even though the state was about evenly divided between the parties, he was proposing a map drawn with the aim of electing 10 Republicans and three Democrats — and that was only because he didn’t “believe it was possible to draw a map with 11 Republicans and two Democrats.”

Mr. Lewis’s conduct will now become de rigueur, not only because naked partisanship has been approved by the court, but because his outrageous comment gave him legal cover for the gerrymander. North Carolina was forced to redistrict in 2016 because the Supreme Court found its earlier congressional map to be a racial gerrymander. Since 1993, the Supreme Court has held that making race the predominant factor in drawing district lines without a compelling reason for doing so violates the equal protection clause of the 14th Amendment. By so openly declaring he was engaged in partisan politics, Mr. Lewis was trying to prove that race did not drive the North Carolina General Assembly’s decisions.

The entire exercise is nonsensical in a place like North Carolina, where about 90 percent of African-American voters support Democratic candidates and about two-thirds of white voters support Republicans. One cannot discriminate against Democrats without discriminating against African-Americans in North Carolina, and vice versa.

So we know what we can expect in North Carolina in 2021, if Republicans still control the legislative branch and thus redistricting (in that state, the governor, who now is a Democrat, plays no role in approving the plans). Republicans will use sophisticated technology to draw a very effective partisan gerrymander. They might even keep redrawing lines every few year s to keep their advantage. They will proclaim loudly and often that their purpose is to help the Republican Party. They will all be instructed not to talk about race.