"Partisan gerrymandering is as old as it is corrosive to a representative democracy. Self-interested politicians have no business making maps with the sole purpose of keeping themselves and their party in power. And yet for decades, the Supreme Court has refused to interfere, unable to agree on a standard to determine when redistricting for partisan purposes violates the Constitution, but -- because of clearer constitutional concerns -- the court has weighed in repeatedly on the problem of race-based redistricting; the justices struck down 2 No. Carolina congressional districts that unnecessarily packed in tens of thousands of extra African-American voters, drawing them out of other districts where they might have made a difference. With a partisan gerrymandering case likely to hit the court’s docket next term, the justices should finally set clear limits on the practice."