AILSA CHANG, HOST:

This week, the Supreme Court will hear cases on whether lawmakers in Virginia and North Carolina rely too heavily on race when drawing congressional districts. The Supreme Court has ruled before on race and redistricting, but it's avoided getting involved in evaluating partisan gerrymandering. That could change all because of a recent decision by a federal district court in Wisconsin. University of Chicago law professor Nicholas Stephanopoulos was a lawyer for the plaintiffs in that case.

NICHOLAS STEPHANOPOULOS: So it was a claim by about a dozen Wisconsin citizens that Wisconsin's current state House district plan was an unconstitutional partisan gerrymander because it deliberately and severely and unjustifiably discriminated against Democratic voters and candidates.

CHANG: And let me just make sure we all understand it. This is partisan gerrymandering, right? I always thought partisanship was the whole point of gerrymandering. That's first what I want to talk about. You know, when does gerrymandering become too partisan to be legal?

STEPHANOPOULOS: So the courts have struggled with that exact question for years. From the founding up until 1986, there was no judicial or legal limit on the extent of partisan gerrymandering that was allowed. In 1986, though, the Supreme Court for the first time recognized a theory of partisan gerrymandering under the Constitution. Now, it's worth noting that even though we've in principle had this lawsuit available for the last 30 years, plaintiffs have never actually won one of these cases.

CHANG: And the idea is, to put it in sort of simpler terms, is people can bring lawsuits to allege that districts are redrawn in a way that favors too much the other party.

STEPHANOPOULOS: Exactly. So, you know, when you draw district lines, there are two techniques that map makers often use in order to benefit their side and to disadvantage the opposition. One of those techniques is called cracking, dividing up the other side's voters among a whole bunch of districts where their preferred candidates consistently lose by a relatively narrow margin. And then the other technique is packing, concentrating the other side's voters in a handful of districts where their preferred candidates win by overwhelming majorities - 75-25, 80-20. And so all partisan gerrymandering is is the use of those two techniques to give one side an advantage and the other side a disadvantage in terms of how their voters and votes in the state translate into seats in the legislature.

CHANG: Have Republicans ever brought partisan gerrymandering cases against Democrats?

STEPHANOPOULOS: Yeah, absolutely. At the moment, there's a pair of major partisan gerrymandering lawsuits against the congressional plan in Maryland, which was designed by Democrats. And there were also major lawsuits against Illinois' congressional and state legislative maps, which were both designed by Democrats. And historically, too, there have been a bunch of Republican lawsuits in plenty of other places.

CHANG: Again, I thought the point of gerrymandering was absolutely to favor the party in power. So could we ever get to a point where parties are redistricting neutrally? Isn't that unrealistic?

STEPHANOPOULOS: So I would say the point of gerrymandering is to gerrymander, but the point of redistricting doesn't have to be to gerrymander. And the easiest way to prevent redistricting from turning into gerrymandering is to give the power to draw district lines to a neutral commission. And many states in the U.S. already do that. Basically all foreign countries that have a similar system to ours also don't let sitting politicians design their own districts.

CHANG: Do you see this Wisconsin case getting to the Supreme Court?

STEPHANOPOULOS: We won't know for sure until the state makes a decision about whether or not to appeal. You know, they don't want to have to redraw their district map unless they absolutely have to. So I think it's likely they'll appeal, and I think it's likely the Supreme Court will decide to hear the case on the merits because it is such a landmark victory and because it does pose very significant national questions about what the test for partisan gerrymandering ought to be.

CHANG: Nicholas Stephanopoulos from the University of Chicago School of Law. Thank you so much for joining us.

STEPHANOPOULOS: Thank you. Transcript provided by NPR, Copyright NPR.