Ever since the Keystone State was called for Donald Trump in the early morning hours after Election Day 2016, it’s been clear that the road to the White House in 2020 runs through Pennsylvania.

So how does today’s landscape compare to what it was then? To find out, I studied the county voter registration numbers from October 2016 to October 2019.

As you’ll see, every section of the commonwealth tells a unique story of the past three years.

A quick note: I explore Pennsylvania’s changing voter trends by tracking the gains one party accumulated in registrations over the other party. For example, R+500 means that the Republican Party gained a net 500 more registered voters in that county than the Democratic Party did over this time period, while D+500 indicates the opposite.

Central

Blair: R+2,664

Centre: R+808

Clearfield: R+3,462

Columbia: R+2,255

Huntingdon: R+461

Juniata: R+870

Mifflin: R+1,249

Montour: R+326

Northumberland: R+2,579

Snyder: R+418

Union: R+291

As you might expect, it’s all red in the center of the state. Given the large Penn State contingent, Centre County’s population is constantly in flux, so Democrats shouldn’t panic at this particular number. That being said, they still could definitely use some of that Obama-era magic among college students next year.

North Central

Bradford: R+872

Cameron: R+200

Clinton: R+1,559

Elk: R+2,047

Lycoming: R+2,866

McKean: R+727

Potter: R+519

Sullivan: R+199

Tioga: R+1,010

This region is also solidly Republican, as expected. While it’s tempting to gloss over Pennsylvania’s equivalent to flyover country, it’s worth noting that even in these extremely rural areas the GOP continues to run up impressive margins.

Northeast

Carbon: R+2,508

Lackawanna: R+6,568

Luzerne: R+6,534

Monroe: R+1,288

Pike: R+607

Schuylkill: R+4,233

Susquehanna: R+858

Wayne: R+875

Wyoming: R+590

As I’ve mentioned before, northeastern Pennsylvania is quietly very essential to statewide contests. In 2016, Hillary Clinton lost 55,373 of the votes Barack Obama got four years before in Lackawanna and Luzerne counties (she ultimately lost Pennsylvania by 44,292 votes).

This should be enormously worrying to the 2020 Democratic presidential nominee, whether it’s Scranton native Joe Biden or not, as the northeast continues to shift toward Appalachia rather than Acela.

Northwest

Clarion: R+1,433

Crawford: R+1,830

Erie: R+2,752

Forest: R+161

Jefferson: R+1,678

Mercer: R+4,306

Venango: R+1,228

Warren: R+1,240

The lakeside county is of course the major player here, and once again Democrats face an Obama-Trump county where they continue to fall behind.

Expect Democrats to focus more attention on Erie this time. In fact, Beto O’Rourke already made a campaign stop there in September. Mercer stands out as well, since it’s one of the four counties (along with Carbon, Elk, and Westmoreland) that’s flipped from blue to red over the past three years.

South Central

Adams: R+2,310

Bedford: R+1,543

Cumberland: D+1,402

Dauphin: D+656

Franklin: R+2,801

Fulton: R+733

Lancaster: D+4,503

Lebanon: R+1,150

Perry: R+780

York: R+7,064

This section of the state is the first, and one of the few, that will give Democrats hope. As previously noted and detailed further below, it appears Philly’s collar counties are becoming so blue they’re spilling over into Lancaster County.

This makes me skeptical that the Trump team’s efforts toward Amish voters is a smart use of resources.

Meanwhile, Harrisburg’s suburbs and exurbs are fueling Dem growth in Dauphin County and even across the Susquehanna River in Cumberland County.

Southeast

Berks: R+5,768

Bucks: D+1,807

Chester: D+11,501

Delaware: D+17,310

Lehigh: R+1,306

Montgomery: D+18,813

Northampton: R+3,699

Philadelphia: R+15,928

Southeastern Pennsylvania is a real “best of times, worst of times” situation for both parties.

Philly’s collar counties are becoming an even deeper shade of navy. Most importantly for the blue side, Bucks County has bounced back toward them, while Chester County could be a majority Democrat county by October 2020.

Yet the Lehigh Valley, especially Berks County, is floating away. A note on Philadelphia: a voter roll update earlier this year is responsible for that movement and Democrats are already approaching their original 700,000-plus voter advantage again.

Southwest

Allegheny: D+12,607

Armstrong: R+2,849

Beaver: R+6,761

Butler: R+3,391

Cambria: R+8,693

Fayette: R+8,743

Greene: R+2,633

Indiana: R+2,483

Lawrence: R+3,623

Somerset: R+3,357

Washington: R+6,666

Westmoreland: R+14,240

Pittsburgh remains a blue oasis in a red sea as the Appalachian ancestral Democrats are still fleeing to the Republican party at a considerable rate. Beaver, Cambria, Fayette, Greene, Lawrence, and Washington counties are all rapidly moving from blue to red. While Democrats can’t write this whole area off, they’re not likely to find much (if any) success here.

Conclusion

“For every blue-collar Democrat we lose in western Pennsylvania,” Senate Minority Leader Chuck Schumer, D-N.Y., asserted back in the summer of 2016, “we will pick up two moderate Republicans in the suburbs in Philadelphia.” His prediction infamously didn’t come true, but in many ways it remains the theory of choice for Democrats.

For example, Clinton cited Franklin & Marshall polling of the Philly suburbs in her 2016 campaign post-mortem “What Happened” to justify her belief that James Comey’s late intervention cost her the presidency.

After shocking the world three years ago, it makes sense that the GOP would roll their eyes at these claims.

In 2018, however, Gov. Tom Wolf and U.S. Sen. Bob Casey, D-Pa., put up monster numbers in Bucks, Chester, Delaware, and Montgomery counties against Trump-like opponents. Yet questions remain as to whether the Dems can win the presidency with such a strategy, and if so, how large of a margin they would need.

As you can see, with a few exceptions, Republicans are gaining everywhere else throughout the commonwealth. Their growth in the Scranton/Wilkes-Barre corridor and the Erie area are especially concerning for Democrats because, unlike the Southwest, these are relatively new trends.

Although if I had to pick one spot that I’ll be watching most closely, I would go with the Lehigh Valley trio of Berks, Lehigh, and Northampton counties. Clinton barely won just Lehigh County, while Wolf and Casey swept all three.

Political observers rightly focus on the small group of suburban voters who hated both Trump and Clinton but swung the former’s way on Election Day 2016. Many of them regret that choice and are at least open to a different Democratic nominee. Lehigh Valley should be a hotbed of these voters and a signal for how the 2020 race is going.

Capital-Star Correspondent Nick Field writes from Bucks County.