What happened in Pennsylvania Monday could swing control of the House in 2018

This is the second time already this year in which a court has thrown out a congressional map. Earlier this month, a three-judge federal panel dumped the North Carolina lines because politics was the primary motivation of Republican line-drawers.

For more context on the Pennsylvania map -- and a look at how the court's ruling could change the makeup of the state's congressional delegation -- I reached out to Jonathan Lai of The Philadelphia Inquirer. Our conversation, conducted via email and lightly edited for flow, is below.

Cillizza: How expected was this ruling on the Pennsylvania map? Or did the striking down of the lines come as a major surprise for the Pennsylvania political world?

Lai: ​​No one's ever certain. But one thing that's been clear from the beginning is that the court is interested in this issue: After a lower state court stayed the case, the plaintiffs asked the [state] Supreme Court to exercise a rarely-used power to take over the case and fast-track it. The [state] Supreme Court did so, saying the case "involves issues of immediate public importance." From that point on, the case moved extremely quickly, and Monday's order came just days after oral argument.

So it's been clear that the court was interested in taking up this issue, and at oral arguments they seemed open to the idea that the map is unconstitutional.

There was also always the question of the partisan makeup of the court itself: Judges are elected in Pennsylvania, and five of the seven Supreme Court justices were elected as Democrats. For a while now, sources on all sides have whispered about the idea that the court might do this. One side cheered the possibility of a "progressive court" stepping in to save democracy, while the other side worried that an "activist court" would legislate from the bench. As soon as the order came out yesterday, we saw immediate accusations of just that.

Cillizza: The next step, politically, is for the Republican state legislature to redraw the map -- and then send to the Democratic governor his approval. How likely are each of those things to happen?

​​Lai: Hard to say. Republicans immediately said they would seek a stay from the US Supreme Court, arguing that the state Supreme Court overstepped.

While they wait to see what happens, they've also signaled that they'd start drawing maps. Assuming no SCOTUS intervention, there are two ways a new map gets drawn: Lawmakers pass a map and it goes to the governor, or the Supreme Court adopts a map. Republican lawmakers seem more interested in having some control over the process, drawing it themselves, rather than leaving it to the court.

What gets tricky is that Tom Wolf, the Democratic governor, has approval over the map --- or a veto. If legislators want to keep the mapmaking out of the hands of the court, they'll have to draw districts in a way that Wolf approves of. That creates strong incentives for Republicans to work with the governor, rather than risk getting shot down.

One question I'm hearing raised: Because Wolf himself is up for re-election this year, is it better for him to veto a map and have no responsibility for it, or to engage with the process and frame it as being bipartisan? We'll see what happens. He tweeted yesterday that he "will not accept a partisan gerrymander," but the spokesman for House Republicans responded that "it sounds as though you (once again) have no interest in working together to craft a new bipartisan map."

Cillizza: This decision lands amid a House Ethics investigation into Rep. Pat Meehan, a Pennsylvania Republican. His district is one of the most gerrymandered in the state. Do Republican line-drawers sacrifice him in the new map?

Lai: ​I'm not really in a position to answer this question, honestly.

What we know is that a new map is likely to include at least a few districts that are more Democratic-leaning or competitive, and that the Philadelphia suburbs are dense[ly populated] and have contorted districts. The area also already has a mix of Republican and Democratic voters, and Meehan's district went for Hillary Clinton in 2016.

But what the new map would do to individual districts or congressmen, I can't say.

Cillizza: What other incumbents, D or R, have to be nervous if/when the map starts getting redrawn, and why?

Lai: ​​Sorry --- same answer as above. There's a lot we don't know yet at this point, including how many districts Republicans might decide to "sacrifice," how many they might make competitive but not Democratic-leaning, etc. We also don't have an opinion yet from the court. Their order Monday said an opinion would follow, and gave only very basic instruction as to how a constitutional map would look. An opinion that explains the unconstitutionality of the current map would guide mapmakers as they draw a new one.

In Monday's order, the Supreme Court said a map "shall consist of: congressional districts composed of compact and contiguous territory; as nearly equal in population as practicable; and which do not divide any county, city, incorporated town, borough, township, or ward, except where necessary to ensure equality of population." Those are among what experts consider to be neutral traditional districting principles.

Cillizza: Finish this sentence: "Republicans currently have a 13-5 edge over Democrats in the congressional delegation. After the 2018 election it will be _______." Now, explain.​

Lai: "short-lived, whatever the margin."

Obviously, we don't know what the map will look like, or the margins. What happens if Democrats have a wave in November? What happens if Republicans sacrifice a few districts but keep their edge? Plus, Democrats in the state are clustered in a few urban areas, meaning the political geography works against them --- a neutral map does not necessarily mean a 9/9 split.

What we do know is that the congressional map is set to be redrawn in 2021 no matter what, since the maps are redrawn every decade after the Census. And Pennsylvania hasn't had enough population growth to keep up with other parts of the country, so we were already on track to lose a seat, going from 18 districts to 17.

[Congressmen] are elected every two years, so the map used in 2018 could also be used in 2020. But a whole new map is just three years away at this point, and who knows what that will bring?