The technical term for this is “gerrymandering” — drawing district boundaries so as to give your own political party an advantage in elections. It's possible because, in a majority of states, politicians are responsible for drawing their own district boundaries after each census.
North Carolina Republicans have gotten quite good at this, as evidenced by the state's 2016 election returns. Republican House members representing North Carolina won 53 percent of the statewide popular vote, but took 10 out of 13, or 77 percent, of the state's congressional seats. If their seat haul had matched their popular vote total, they would have taken just seven out of 13 House seats.
The state's Republicans are vowing to overturn the ruling. They also deny that their district boundaries are the result of gerrymandering. “A gerrymander is by definition and common understanding a strange-looking monster drawing,” North Carolina GOP Chairman Robin Hayes said in a statement. “This map is clearly not that.”
It's true that odd-looking congressional districts, with squiggly lines and protuberances sticking out everywhere, are often a surefire sign of gerrymandering. But the North Carolina case indicates how savvy political operators can game the system while keeping districts looking fairly tight and compact. To understand how they did it, take a look at the map below.
I started with a map of precinct-level 2016 presidential vote results compiled by Ryne Rohla, an economics doctoral student at Washington State University. This gives a pretty good sense of where Democrats (blue) and Republicans (red) are concentrated in the state.
I've rather crudely superimposed on that the current boundaries of North Carolina's U.S. congressional districts.
Now we can see how district boundaries snake around and through Democratic-leaning areas. Let's focus on a few of them, starting with the 2nd Congressional District.
George Holding (R) won the 2nd District with 57 percent of the vote in 2016. One notable feature of the district's border is how it snakes around the 4th District to the east. Essentially the entire city of Raleigh is packed away into the heavily Democratic 4th District, which David E. Price (D) won with a commanding 68 percent of the vote.
By packing the region's Democrats into the 4th District, North Carolina Republicans ensured that they held a small but substantial majority in the 2nd District.
Instead of packing all your opponents into the same district, however, sometimes it's more optimal to split them up into several. The map below shows exactly how Republicans did that in the city of Greensboro.
Like Raleigh, Greensboro is a Democratic stronghold. But in this case, Republicans drew the border between the 13th District and 6th District right through the middle of the city, effectively splitting the Democratic population in two and ensuring that Democrats would have difficulty competing in either district.
As a kind of bonus, they packed all of nearby Winston-Salem's Democrats away in the 5th District. Had all of Greensboro's and Winston-Salem's Democrats been in the same district, there's a very good chance it would have gone blue. Instead, by dividing that population up into three districts, Republicans were able to neutralize Democratic power in that part of the state.
These examples illustrate how gerrymandering isn't simply a question of shapes on a map, as North Carolina Republicans seem to imply, but of intent. The party set out explicitly to disenfranchise Democratic voters, and that's exactly what they did.
It's also worth pointing out that this isn't strictly a one-sided phenomenon. Given the opportunity, Democrats will happily gerrymander their opponents into oblivion, as the example of Maryland shows.
For this reason, reformers are increasingly demanding that redistricting power be taken out of the hands of politicians. In a small number of states, independent commissions now do that job.
The Supreme Court has also shown a renewed interest in whether strictly political gerrymandering, of the North Carolina variety, violates voters' constitutional rights. A ruling on the first of those cases is expected before June.