“For a court that says they don’t want to look political, they’re doing their level best to undercut that,” said Pamela Karlan, a law professor at Stanford and a former Justice Department official in Democratic administrations.

She noted the court’s decision came as a nationwide midcycle redistricting fight continues to play out in states throughout the country. The efforts by Republican and Democratic legislatures were spurred by President Trump’s demands to secure new House seats, in seeking to keep his party’s razor-thin majority.

The justices had already cleared the way for the new maps in both Texas and California, Ms. Karlan noted.