Why the new Pennsylvania map is a 'huge' deal in the fight for House control

Washington (CNN)On Monday, the Pennsylvania Supreme Court redrew the state's congressional lines in advance of the 2018 election. (The court had previously ruled that the map drawn by Republicans earlier in the decade was driven mainly by partisan consideration and therefore in violation of the state's constitution.)

The new map will fundamentally rejigger the state's politics and, at first glance, will make Democrats much more competitive in a state that has leaned their way for most of the last two decades.
For more perspective on the Pennsylvania map -- and what it means in both Pennsylvania and in the fight for control of the House nationally, I reached to out my friend Jonathan Tamari, the national political reporter for the Philadelphia Inquirer. Our conversation, conducted via email and lightly edited for flow, is below.
Cillizza: How did we get to this point? And is this the final final map for the 2018 election?
    Tamari: This is one of those stories that show how sometimes big things in politics take a long time to happen -- and then seem to happen all at once.
    In many ways, the fight traces back to the tea party wave of 2010. It gave Pennsylvania Republicans big wins in congressional races, and control of the Pennsylvania statehouse just as it was time to draw up new congressional maps. The GOP promptly took that control and made maps that effectively locked them into those competitive Congressional seats. Even with Barack Obama winning PA in 2012, and Dems winning about 51% of the congressional vote, they made zero gains in Congress -- and held just five of 18 seats.
    In 2015, though, Democrats won a majority on the state Supreme Court, and this year the court took up the gerrymandering debate. The court threw out the existing map as unfair in late January and ordered the GOP-controlled legislature and Democratic governor, Tom Wolf, to come up with a new plan. Of course they didn't compromise, and the court imposed its own map Monday. The result: in less than a month, the court has scrambled the political math that could affect control of the entire US House.
    Cillizza: This map seems to be very friendly for Democrats. Fair?
    Tamari: Yes. Democrats argue that this is basically establishing a PA map as it should be: almost evenly divided in a state where the vote typically splits close to 50-50. They'd add that this comes after years of facing an unfair GOP advantage, and that competitive districts are good for everyone, regardless of party.
    But when it comes to immediate electoral implications, I think few independent analysts thought it would turn out this well for Democrats -- who face natural geographic disadvantages, regardless of any gerrymandering. As some real smart analysts have said (among them, the Upshot crew at the NYT and Cook Political Report's Dave Wasserman) there were a number of decisions in these maps that could have reasonably gone either way. In almost every instance, they went in the Democrats' favor.
    You could make a fair case for just about all of them individually, and the map overall is inarguably more compact, contiguous and rational than what preceded it. It's not as if the court drew up a tortured Democratic mirror of the old GOP version. But add up all the decisions and this map helps Democrats more than almost anyone expected.
    Cillizza: What's the fallout been -- if any -- from the map so far? Do we expect retirements? Incumbents moving districts?
    Tamari: People were still trying to get their heads around it even late Monday night. Folks who have been working in politics for a long time were basically reduced to saying "this is crazy."
    I think a few key players are going to have to make big decisions that start the domino chain of decisions. Most immediately, Democrats are hoping Conor Lamb can pull off a big upset in a special election in western PA next month -- but even if he does, he might have to move districts by November to survive.
    In Philly, one incumbent, Democrat Brendan Boyle, has a very different district, and will have to decide if he stays in his current seat or moves over to neighboring Montgomery County (which he partially represents now, but is cut out of his new district). Depending on where he goes we could see a Democratic free-for-all for his open seat in Philly, or the one in Montgomery. A bunch of people who had lined up to run for an open Philly seat being vacated by Democrat Bob Brady suddenly are staring at two incumbents ahead of them and no opening (unless Boyle moves).
    Republican Scott Perry is one incumbent who, out of the blue, faces a much tougher district. Same with the GOP's Keith Rothfus in western PA. But can Democrats find good challengers fast enough to take advantage? These guys weren't even on the radar two days ago.
    Cillizza: Take a step back. How big a deal is this new map for Democrats trying to take back the House? For Republicans trying to keep it?
    Tamari: Huge.
    Under the old map, Democrats had one really good chance to flip a GOP seat and two or three others that were possible, but tough. Now you have to make Democrats the favorite to gain at least three Pennsylvania seats, and maybe more given the political environment this year. If a major wave shapes up, you could even see them going from five seats in Congress to 11.
    In another year, they'd be unlikely to fare that well and Republicans would have a good shot at a majority of the seats in good GOP years. But for 2018, you combine this new map with the traditional midterm backlash against the party in power, the current Democratic energy and presidential approval ratings, and suddenly, the state that effectively sealed President Trump's victory could be on the leading edge of Democrats' push to win back the House.
    Cillizza: Finish this sentence: "In 2019, at the start of the new Congress, the partisan breakdown of the Pennsylvania delegation will be _________." Now, explain.
    Tamari: "Nine-nine."
    Democrats hold the two seats in Philly and one centered on Pittsburgh (duh). They gain three seats in the Philly suburbs (based in Chester, Delaware and Montgomery counties). They gain a Lehigh Valley seat (where Republican Charlie Dent is retiring) and hold Matt Cartwright's competitive seat in northeast PA. And given the wind at their backs they pick up one more of the three real competitive races left on the map.
    Why not more? I think it's late for Democrats to go out and find quality candidates to take on those incumbents. With this caveat: I've covered both politics and sports, and the one constant is that my predictions are terrible in both.