A strengthened conservative U.S. Supreme Court majority with the addition of Justice Brett Kavanaugh could spell the end of constitutional challenges to partisan gerrymandering.

The court is likely to take up the issue again this term in a North Carolina case, and reach a decision next year at the earliest—too late to influence the congressional midterms in less than a month.

Before, there were four justices who thought “there were viable standards to root out partisan gerrymandering,” four who thought...