It doesn’t get a lot of attention next to the presidential race, but Republicans have a fighting chance to retake control of the U.S. House next year. Dozens of Democrats sit in seats President Trump carried in 2016, and the GOP still has a built-in structural advantage due to geographic self-sorting and how some districts are drawn. But some of that advantage disappeared this week, when a three-judge panel approved a new congressional map for North Carolina to replace the state’s previous Republican gerrymander.

It’s been a busy year for North Carolina district maps. In September, North Carolina’s state-legislative map was thrown out for violating the state constitution’s “free elections” clause. Within the month, Democratic-backed plaintiffs filed a similar lawsuit against the state’s U.S. House map, which was drawn to maximize the number of Republican districts. In October, a majority-Democrat panel of judges found that the map showed signs of “extreme partisan gerrymandering” and issued an injunction against it, and the Republican legislature passed a new map in mid-November. The Democratic plaintiffs argued that the boundaries were still not fair enough, but on Monday, the judges ruled in favor of the map, which will now be used for the 2020 elections.

Let’s dive into the partisanship of the new map. Thanks to Daily Kos Elections, which has already calculated the results of the 2016 and 2012 presidential races (among other recent elections) in each of the new districts, we’ve calculated FiveThirtyEight partisan leans for each of the new seats, and the new map does significantly alter the partisan composition of several North Carolina districts. That means that, instead of 10 pretty safe Republican districts and three pretty safe Democratic ones, North Carolina now has eight fairly Republican-leaning districts and five fairly Democratic-leaning ones.

Two red districts in North Carolina just became blue The FiveThirtyEight partisan leans* of North Carolina’s congressional districts, before and after court-ordered redistricting in 2019 District Old Partisan Lean New Partisan Lean 1st D+35 D+10 2nd R+13 D+19 3rd R+24 R+24 4th D+35 D+29 5th R+18 R+36 6th R+16 D+18 7th R+18 R+20 8th R+15 R+10 9th R+14 R+13 10th R+24 R+38 11th R+28 R+17 12th D+37 D+34 13th R+10 R+36 *Partisan lean is the average difference between how a state or district votes and how the country votes overall, with 2016 presidential election results weighted at 50 percent, 2012 presidential election results weighted at 25 percent and results from elections for the state legislature weighted at 25 percent. Note that FiveThirtyEight’s current partisan leans do not yet incorporate the results of the 2018 election. Source: Daily Kos Elections

The two districts whose partisan lean changed hues as a result of the new boundaries are the 2nd and 6th. Instead of being an R+13 seat encompassing the exurban and rural areas around Raleigh, the 2nd District now covers Raleigh and its immediate suburbs and is now 19 points more Democratic-leaning than the country as a whole. Former state Rep. Deborah Ross, the Democrats’ 2016 U.S. Senate nominee, headlines a crowded field of Democrats running for the seat, while current Republican Rep. George Holding has said he will not run here again. Similarly, the 6th District has also gone blue — from R+16 to D+18 — by swapping several rural counties for urban areas like Greensboro. Incumbent Republican Rep. Mark Walker sounds unlikely to run here again, too; instead, he is reportedly considering primarying a Republican incumbent for U.S. Senate. Meanwhile, Democrat Kathy Manning, who lost a bid for the 13th District in 2018, looks like a formidable contender for the new 6th.

The new map makes it very likely that Democrats will pick up two House seats in North Carolina in 2020. That’s important because it makes Republicans’ quest to regain House control — or at least eat into Democrats’ majority — that much harder. In effect, Republicans need to flip two additional Democratic-held seats just to stand pat in the House.

But many Democrats still aren’t satisfied with North Carolina’s new map. In pressing the legal case against it, National Democratic Redistricting Committee chair Eric Holder complained that the redrawn map “simply replaces one partisan gerrymander with a new one.” And he has a point — the new map does still give an advantage to Republicans, albeit a smaller one than the old map. Under the old lines, the median district by partisan lean was 10 points more Republican-leaning than the state as a whole. And under the new lines, the median district is 7 points more Republican-leaning than the state as a whole.

If you’re a fan of a roughly proportional map — a.k.a., one where the share of seats a party wins is aligned with its statewide vote share — that’s a problem, as is the fact that the map is virtually unresponsive to changes in the national mood. To see this in action, just compare the share of congressional seats Republicans would win under different national popular vote scenarios in North Carolina to Pennsylvania, which got a new court-ordered congressional map in 2018. In that case, the Democratic-controlled Pennsylvania Supreme Court appeared to go out of its way to create competitive districts that would ensure the makeup of the state’s congressional delegation changed with the political winds. North Carolina’s map appears less responsive.

As you can see in the chart above, as Republicans or Democrats do better in the national popular vote, we would expect them to flip multiple seats in Pennsylvania. For example, assuming congressional results track exactly with partisan lean, we would expect Democrats to win eight out of 18 seats in a D+1 environment, but 10 of 18 seats in a D+6 environment and just five of 18 seats in an R+5 environment.

But in North Carolina, partisan lean implies that Republicans would win eight out of the 13 new districts in a Republican wave year (R+10) … and in a neutral political environment … and in a Democratic wave year (D+9). In fact, Democrats would have to win the national popular vote for U.S. House by 13 percentage points to win a majority of North Carolina’s U.S. House seats (again, assuming the results tracked exactly with partisan lean).

Plaintiffs could have appealed the case to the North Carolina Supreme Court in hopes of getting a more competitive map, but they declined to do so on Monday, citing the fact that candidate filing is already underway. And of course the maps will be redrawn in North Carolina — and everywhere else — starting in 2021, so both sides will have another crack at drawing the map soon.