As recently as last summer, Pennsylvania Democrats were struggling to pull themselves off the mat.

After six straight presidential victories, the Keystone State suddenly turned red and played a pivotal role in Donald Trump’s 2016 Electoral College victory. On top of that, the gains Republicans were making in voter registration throughout 2016 were continuing into 2017.

Over the past 12 months, however, momentum has been on the Democrats’ side.

For instance, during my last update nearly a year ago, Democrats had 808,974 more registered voters statewide than the Republicans. Today their advantage is 812,451.

Last time, the GOP held every spot on the Top 10 list of gains. This time, the Dems come out ahead in a 6-4 split. Back then, just three counties saw an increase in Democratic voters; now, there are 14 such counties.

The primary culprit seems to be enthusiasm. After all, there’s nothing more motivating than being out of power and the opposing party in Congress has picked up seats in nearly every midterm election since the Civil War.

There’s also evidence to suggest a generational surge. A recent TargetSmart review of efforts by the Parkland survivors to register younger voters saw a 16 percent increase among Pennsylvania’s 18- to 29 year-olds – the commonwealth ended up finishing first among the 40 states surveyed.

In order to gain a more complete view of recent shifts and what they can mean for November, I compiled the following updated Top 10 list.

A reminder: this list concerns the gains one party accumulated in registrations over the other party in the past year. For example, R+500 means that the Republican Party accumulated 500 more registered voters in a county than the Democratic Party did over this time period.

10. Monroe - R+1,364

While plenty of attention is paid to ancestral Democrats in the Southwest leaving the party, Northeast PA is quietly getting redder.

Monroe remains a blue county – and a suddenly important one, as the new Congressional map splits it between PA-7 and PA-8. The former was the home to recently retired moderate Republican Charlie Dent while the latter is Matt Cartwright’s new district.

9. Luzerne - R+1,482

Speaking of the Northeast, Luzerne County and its town of Wilkes-Barre is home to thousands of Obama/Trump voters that made the difference two years ago. The 45th President’s strength there is why Cartwright is one of the few endangered Democratic incumbents this cycle.

To cap off this point about the Northeast, only one county shifted party allegiance over the past 12 months. It was Carbon, smack dab between Luzerne and Monroe, where the registration advantage switched from Dem to GOP.

8. Washington - R+1,540

Those ancestral Appalachian Democrats are still real, though, and they continue to peel away at a rapid pace. Luckily for US Rep. Conor Lamb, his new district excludes Washington in favor of Beaver (where Dems are fleeing at a slower clip) and part of Allegheny. In fact, a recent Monmouth University poll actually gives the newcomer a 12-point over fellow Congressman Keith Rothfus.

7. Philadelphia - D+1,919

Contrary to popular belief, Democratic gains aren’t limited to large cities. Allegheny fell far short of this list (D+755) and Philly actually needed a late surge to even get into the Top 10.

Hillary Clinton proved that one can’t just rely on Philadelphia and Pittsburgh when campaigning in the commonwealth. Nonetheless, high turnout in the City of Brotherly Love remains crucial for Dems as they hold a whopping total registration advantage of 682,303 voters there.

6. Lancaster - D+2,126

If one entry sticks out at first glance as an outlier, it’s this one. Upon further review, though, it begins to make sense. While Trump ran up the margins in many traditionally red areas, his performance in the South Central portion of the state was just par for the course.

The culprit just may be highly religious voters. Sure, Trump has held onto most of this constituency but there remain exceptions. Perhaps evangelicals are more forgiving of the New Yorker’s colorful personal life than the more traditional Mormons of Utah or the Amish in Lancaster.

5. Bucks - D+2,408

Arguably the most heartening news for the Democratic Party comes out of Bucks County. Last year, it placed tenth on the list of Republican gains as the margin slipped to D+6,640. Now it stands at D+9,048.

The Dems can’t afford to lose this bellwether SEPA county, home to one of the country’s most contested Congressional districts in PA-1. Incumbent GOP Rep. Brian Fitzpatrick’s battle with Democratic nominee Scott Wallace is likely to be the fiercest in the commonwealth and a worthwhile barometer for the Dems’ odds of capturing the House.

4. Westmoreland - R+2,693

PA’s largest Southwestern county will be red before too long. Three years ago, the county’s margin was D+26,753. It currently stands at just D+4,592.

Despite their overall gains in the state, the day when the Democratic registration advantage in SWPA is whittled down to lonely Allegheny is fast approaching.

3. Chester - D+4,314

In order to make up for those disappearing Southwest Dems, the party needs to make gains in the Southeast. In that same three-year span, they’ve picked up about 8,000 net registrations here.

Chester remains the last SEPA holdout where Republicans outnumber the competition but their lead is steadily eroding. This Romney/Clinton county is slowly but surely turning blue. Just ask Ryan Costello, who chose to pack his bags and head home rather than defend his new Chester-heavy district.

2. Delaware - D+6,329

The top two entries on this list are blue SEPA counties. Delaware is also home to the new 5th Congressional District. Even without the scandal that caused him to drop out, Patrick Meehan would’ve been hard-pressed to defend this seat.

In the end, Delaware was only outpaced by its neighbor to the north.

1. Montgomery - D+7,078

Back in 2015, Scranton made Lackawanna the Democrats’ third-strongest PA county. Now that honor belongs to Montgomery County.

Out with the lunch pail-carrying union Steelworkers and in with the pink-hatted, #Resistance warriors. Amidst the blue Southeast, Montco is practically navy. Any statewide Dem candidate worth their salt is going to want to turn out as many voters as possible here.

It goes to show that although the commonwealth contains dozens of disparate trends, the Acela-Appalachian divide is alive and well.