What's behind the Republican surge in Pennsylvania voter registration?

Plus, a potential surprise brewing in the Philly suburbs

Republicans are surprisingly serene about Pennsylvania (the most likely tipping point state) because of the steady gains that the party has made in voter registration. Since 2020, the state’s Democratic registration advantage has been cut in half, from 7.5% to 3.7%. That state’s registration still tilts more Democratic than its presidential environment, but that’s changing rapidly.

Thanks to ChatGPT, I was able to quickly extract numbers from this graphic for analysis. First, I wanted to answer the question of if the registration shifts we are seeing are all just a lagging indicator. After all, people typically update their vote choice faster than they change their party. It may be years after switchers first start voting for Republican or Democratic candidates consistently before they admit to themselves they’ve switched parties. And something like this does indeed appear to be happening. The 2024 registration numbers are a lot more aligned with the 2020 election results than the 2020 registration numbers were. They’re tied very closely together both years, but the R-squared — an indicator of statistical significance where 1 is a perfect fit — has gone from 0.8175 to 0.9203.

The Democratic registration advantage in Pennsylvania is mostly a function of rural counties being far more Democratic by registration than they vote. That makes rural registered Democrats who haven’t switched yet one of the most coveted persuasion targets for Trump—especially if they voted in-person on Election Day in 2020 and haven’t voted in Democratic primaries recently.

The vast majority of Pennsylvania counties—the ones undergoing a long-term Republican shift—are ones where Trump in 2020 outperformed Republican registration. Meanwhile, the most suburban and college-educated counties are the ones where, on net, Biden outperformed Democratic registration, or where more Republicans voted for him.

In the state’s southwest Appalachian corner, the disconnect is extreme: Greene and Fayette Counties were 42 and 40 points respectively more pro-Trump in their vote shares than they were by registration in 2020. There are lots of real, live “ancestral Democrats” still living in these counties.

But the registration gap has narrowed most since 2020 in these two counties—with a 15.7 point net GOP shift in Fayette and 15.2 points in Greene. And to illustrate the point further, the more Trump in 2020 overperformed Republican registration, the more that registration shifted in that county in the last four years. The relationship is near-perfect, with an R-squared of .8876.

This can technically go in both directions—Democrats surging in registration to match Biden margins in blue counties and Republicans doing the same in Trump counties. But it largely hasn’t, hence Republican optimism. The intercept on the chart above is 2.2 points. Translated, that places that were already well-balanced in 2020 terms of both registration and vote share tended to get more Republican by registration over the last four years, by about 2 points. Just four counties statewide—three of them suburban Philadelphia counties and one outside Harrisburg—shifted left by registration, but all of them had a solid surplus of registered Republicans, the opposite of the red rural counties.

Much of the registration shift is simply voter registration coming into stronger alignment with how people actually vote. But there also may have been a slight Republican shift on top of that. But beyond that, was there a pattern to how counties shifted more or less than expected that can tell us about the potential for changing coalitions in 2024?

What I found is that there was indeed a geographic pattern, with some surprising results.