As we all know, election night 2016 effectively ended when Pennsylvania was called for Donald Trump by the narrowest of margins–a mere 44,000 votes out of more than six million cast. The reason that this came as a surprise was that Pennsylvania has long been reckoned as part of the solid bloc of blue states in the Northeast. Before 2016, it hadn’t supported a Republican for president since 1988.

One big reason for Pennsylvania’s swing to the Democratic side is that the Philadelphia suburbs have undergone a dramatic transition from red to blue. For years, they were a classic bastion of moderate Republicanism. But these moderate suburbanites increasingly found themselves out of place in a party that was shifting hard right, especially on social issues. These areas swung over to Bill Clinton in 1992, enough to allow Clinton to win the state. They’ve been a reliable part of the Democratic coalition since.

One county, however, has largely bucked this trend until recently–Chester County, south of Philadelphia. It was the only one of the three suburban Philadelphia counties that Clinton didn’t win even once. However, the Republican margin gradually narrowed, and in 2008 Barack Obama became only the third Democrat to win it since 1912. It narrowly voted for Mitt Romney in 2012, but swung hard to Hillary Clinton in 2016, with Hillary winning by over nine points.

Despite this, Republicans still do fairly well at the state and local level. Additionally, much of the county is represented in Congress by a Republican, Ryan Costello, in the 6th District. However, this weekend, he decided to give up his bid for a third term. He did so after the Pennsylvania Supreme Court tore up the old congressional map and replaced it with a new map that would have made his chances for winning reelection difficult at best.

For his first two terms, Costello represented one of the most blatantly gerrymandered districts in the nation. Look at a map here.

Costello's old district (image courtesy National Atlas, part of public domain)
Costello’s old district (image courtesy National Atlas, part of public domain)

The district took in most of the more populated northern portion of Chester County, then wound its way through western Montgomery County before extending a tendril to heavily Republican Lebanon–an area that hasn’t supported a Democrat for president since 1936–by way of some rural territory outside Reading.

Simply put, this district had no rational basis. It represented a desperate attempt by the Republican-controlled state legislature to hold back the growing Democratic trend in the Philadelphia suburbs. But as we all know, there’s only so much packing and cracking you can do when the demographics are moving against you. Mitt Romney barely won it in 2012, and only then because he ran it up in Lebanon. Hillary Clinton narrowly won it in 2016.

Incredibly, this is the second time that the GOP tried to stick a finger in the dike and keep the 6th in their hands. This is how it looked from the time it was created after the 2000 census.

The 6th District, as it looked from 2003 to 2013 (image courtesy National Atlas, part of public domain)
The 6th District, as it looked from 2003 to 2013 (image courtesy National Atlas, part of public domain)

The original 6th twisted and wound its way through the outer Philadelphia suburbs in an effort to keep its first congressman, Republican Jim Gerlach, in Washington. And yet, despite their best efforts, Gerlach barely won after the seat was created in 2002, and faced three consecutive tooth-and-nail battles for reelection. John Kerry won this district in 2004, and Obama won it going away in 2008.

After Gerlach won in 2010 and 2012 without serious difficulty, he handed it to Costello in 2014. But just when it looked like Costello was settling in, the state supreme court ruled the post-2010 map was an unconstitutional political gerrymander. When the state legislature refused to create a replacement, the state supreme court drew its own map.

That new map lopped off the 6th’s heavily Republican tail into Pennsylvania Dutch Country. In its place, it absorbed the rest of Chester County, while picking up almost all of heavily Democratic Reading. This dramatically altered the 6th’s demographics. While Hillary barely carried it 48-47 in 2016, the new district would have gone for Hillary by a 52-43 margin–due almost entirely to Chester County.

Costello was already facing the fight of his political life against Democrat Chrissy Houlahan, a retired naval officer and the former chief operating officer of shoe company AND1. But when the new map came out, most political handicappers moved the race to “toss-up” or even “lean Democratic.” However, Nate Cohn of The New York Times concluded that Costello was in “very serious trouble,” and openly wondered if he would even run again.

Costello responded by throwing a tantrum. He openly supported an effort by Republican state lawmakers to impeach the five state supreme court justices who voted to overturn the old map.

But just days after the federal Supreme Court refused to hear a last-ditch Republican challenge to the state supreme court map, City&State Pennsylvania, a news organization that covers Pennsylvania politics, detonated a bombshell–Costello wasn’t running for a third term.

It turns out that Costello’s gung-ho support of the unprecedented power grab represented by the impeachment threat was just for the cameras. Republican sources noticed that Costello was only making a “hurried and half-hearted effort” to ramp up his reelection campaign. He almost missed the deadline to submit petitions to qualify for the Republican primary. Reportedly, Costello didn’t even know if he’d stay in the race.

On Saturday night, a source familiar with Costello’s thinking told CNN that Costello was definitely going to pull out of the race before the May primary. While the timing was up in the air, this source said that the pullout was “going to happen.”

Costello’s retirement puts the GOP in a sticky wicket. Only one other Republican, local attorney Greg McCauley, even filed before the deadline. While this effectively hands McCauley the nomination, he’s going to have his work cut out for him to overcome a huge fundraising gap with Houlahan. Additionally, according to his Facebook page, he was initially planning to run in the old 7th District–which is now the 5th District–before the map was thrown out.

These factors, combined with the much bluer hue of the new 6th, this was enough for Roll Call to move the race for this district from “tilts Democratic” to “likely Democratic.” It’s likely that others will follow suit. The new map already assured that the new 5th–which would have been Hillary’s third-best district in the state–would go Democratic. Barring anything unforeseen, it looks like the Democrats are about to erase the last smudge of red from the Delaware Valley’s congressional map.

While Houlahan has to be the favorite in this race, we can’t get complacent. After all, most of Chester County’s elected officials are still Republican, so there’s a lot of history to overcome. She’s going to need a lot of help to convince this district’s voters to break long-standing habits and vote for a Democrat. Let’s help her finish this–click here to donate.

(featured image courtesy Costello’s Twitter)