Brandon Finnigan:
In recent years, the state of Pennsylvania has been pithily described as “Lucy’s Football” — as a place where, however favorable the winds might seem, the Republican party’s aspirations are always thwarted. In this piece, I will make the case that, while this trend has certainly been apparent for the last couple of decades, it is by no means destined to continue forever.
In making this case, I will look at the recent electoral history of the state, examine recent changes in voter registration, analyze demographic data provided by the U.S. Census, hone in on primary-season participation at both the county and municipal levels, and take into account recent polling (as of July 16, 2016). In so doing, I shall demonstrate that not only is Pennsylvania a rare brightening prospect for the GOP, but that it may in fact prove uniquely fitting for the party’s 2016 nominee, Donald Trump.
For the record, I consider myself to be a Republican, albeit one for whom this election cycle has been jarring, nasty, and clarifying. As a result, writing this piece has been bittersweet. I’ve spent the better part of a decade obsessing over the prospect of Pennsylvania trending red — indeed, it has been the one thing I’ve thought and written about to the point of mania — but now, at the point at which it seems likely to happen, I am not sure how to feel about it.
Anyhow.
AN INTRODUCTION AND A LITTLE HOUSEKEEPING
Maps
At the Decision Desk, we prefer to display election returns in a format that illustrates where the voters actually live in a given state. Here, for example, is a traditional map of Pennsylvania:
And here is what the most populated counties look like when adjusted to reflect their share of the overall vote. I will use this latter model for election results and changes in voter registration: 
As you can see, the Philadelphia metropolitan area explodes in size, while most of central Pennsylvania is squeezed out of existence. All labeled counties make up at least 1 percent of the total statewide vote. 
Terminology
You’ll see the following phrases used frequently, so here’s a quick explainer:
The “T” and Pennsyltucky — The non-urban regions of Pennsylvania between Pittsburgh and Philadelphia, nicknames earned from political consultant James Carville’s famous analysis of the state.
The Collar — The four suburban counties that encircle Philadelphia proper: Chester, Delaware, Montgomery, and Bucks.
Bidenland — a stretch of more blue-collar (and unevenly improving economically) counties due north of the Collar that include the municipalities of Scranton, Carbondale, Wilkes-Barre, Allentown, and Bethlehem. I’ve nicknamed the region this because it is the birthplace of our vice president, and reflects the sort of Democratic voter, once more loud and dominant, that has kept the share of the white vote in the North less Republican than in the South.
Main Line — A corridor of very wealthy suburbs stretching out of Philadelphia into Chester, Delaware, and Montgomery Counties. Historically Republican, they have taken a sharp leftward turn in the last 20 years.
A BRIEF ELECTORAL HISTORY OF PENNSYLVANIA
The 2000 Presidential Election
As the 1990s progressed, Bill Clinton enjoyed increasing support in the Philadelphia suburbs that had once been a hotbed of Republicanism. Clinton also enjoyed strong popularity with white, blue-collar voters in Erie, Scranton, and Pittsburgh. When, in 2000, Al Gore ran to replace him, the broad assumption was that Clinton’s vice president would be able to carry on the Democrats’ two-cycle winning streak. He did:
Thanks mostly to big margins in Philadelphia and in still-blue metropolitan Pittsburgh, Vice President Gore defeated Texas governor George W. Bush by a margin of about 205,000 votes. Though he lost, Bush did well in central Pennsylvania, sweeping Lancaster and York by wide margins. He was also competitive in Pittsburgh’s suburbs, which would grow to become a Republican asset in subsequent elections. 
The 2004 Presidential Election
In 2000, President George W. Bush hadn’t campaigned much in Pennsylvania. But that changed in 2004. During Bush’s reelection campaign, the Republicans committed millions of dollars and millions of volunteer hours across the state. As a result, the GOP managed to drive down the Democrats’ overall margin to under 2 percent statewide (140,000 votes). Nevertheless, Pennsylvania voted more Democratic than the country as a whole — by about five points.
As you can see from the chart above, the Democratic nominee, John Kerry, secured large margins in Philadelphia city, won three out of four of the Philadelphia Collar Counties (Delaware, Montgomery, and Bucks), and maintained the long-running Democratic edge in the Pittsburgh media market. By contrast, Bush dramatically drove turnout in the central part of the state and made inroads in Erie, Lackawanna, and Luzerne Counties. While Kerry did manage to win Pittsburgh, Bush improved on his 2000 performance in Westmoreland, Washington, and Fayette Counties. 
The municipal level reveals these changes a bit better: Various townships in the Pittsburgh area are turning varying shades of red (watch them especially in the next two such maps). Bush’s inroads in the northeastern cities, such as Scranton, Wilkes-Barre, and Allentown are more obvious here. The region that the moved away from him was the outer and middle collar around Philadelphia, particularly that Main Line area. 
The 2008 Presidential Election
By the time that the 2008 election rolled around, President Bush’s approval rating had slipped into the 30s, the nation was in the midst of an economic meltdown, the mortgage bomb had finally gone off, and the Democratic party had nominated a young, energetic African American who drove up turnout to historic levels. In 2008, Barack Obama won Pennsylvania by a decisive 10.3 percent margin:
