And it’s not true that Democrats showed up to the polls while Republicans stayed home, either — turnout was high across the entire state, including in Republican areas.

So the rural areas making up Red Pennsylvania shifted further to the right as cities cemented themselves as the anchors of Blue Pennsylvania and suburbs continued their long march to the left.

“Sometimes you think, ‘Wow, can you get more polarized?’ In some ways, the answer is yes. We’ve seen that in the last race,” said Chris Borick, a political science professor at Muhlenberg College in Allentown.

This analysis uses certified election results for the more than 9,000 precincts in Pennsylvania, providing the most complete, granular geographic picture available of official 2018 election results. A comparison with previous years reveals an ongoing division of the state, especially over the last decade.

Pockets of blue have been disappearing from Central Pennsylvania, and areas that previously leaned Republican have now become solidly so.

In Southwest Pennsylvania, hemorrhaging people and jobs, a one-time Democratic stronghold has turned Republican.

In the suburbs, especially outside Philadelphia, a mix of Republican and Democratic votes have become more concretely Democratic.

Visually Comparing 2014 and 2018 Move the slider in the middle to compare the results of the 2014 and 2018 gubernatorial races. 100% D 50% D 0% 50% R 100% R SOURCE: Pa. Dept. of State NOTE: Areas in gray indicate missing data. See methodology at the bottom for more information.

“We often talk about the sorting of America, and how we tend to now congregate even more amongst those like us,” Borick said. “When I see data like this, I think it’s prime evidence of just that fact.”

That geographic sorting is a national and international trend that has profound implications for politics and governance, said William Galston, a senior fellow at the Brookings Institution whose research includes reports on geographic polarization and the Democrats’ path to victory in 2020.

“Wherever you look, the center of the populist revolt is in the small towns and rural areas,” he said. “The center of the resistance to that is in the big cities.”

In Harrisburg, lawmakers worry that middle ground is eroding beneath them as their voters push them into their respective corners. While compromise is still possible, they say, they warn of Congress-like gridlock.

And the map is increasingly perilous for Republican candidates running for higher office.

Traditionally, the path to statewide victory has run through the Philadelphia suburbs. To win the state, President Donald Trump defied the trend by winning just enough votes there and winning or closing the margins in historically Democratic areas like Northeast Pennsylvania.

But the midterm results showed possible cracks in that coalition and a return to the longer-term trend, with Democrats up and down the ballot performing well in the same counties that delivered Trump the state in 2016.

The 2018 election results suggest Trump’s 2016 victory in a handful of key states, Pennsylvania chief among them, “may well have been a one-off in response to a very particular, special set of circumstances,” Galston said.

Moving forward, said Galston and Brookings co-author Clara Hendrickson, geographic sorting and polarization make it easier and more effective than ever for politicians to focus on mobilizing their specific bases, rather than persuading swing voters.

“There’s a clear temptation now for candidates to sort of double-down on a strategy of mobilizing the geographic base, but we’re not even sure if that will work in 2020,” Hendrickson said. “And it is certainly likely to produce a legitimacy crisis within our democracy that is dangerous.”

Galston similarly warned of the dangers of deepening divisions. “If you’re only governing for one part of the country, the other part of the country is going to get really angry,” he said. It’s unclear what would slow or reverse the trend.

Blue Pennsylvania is bluer and better-defined than ever. Red-Pennsylvania is redder and better-defined than ever. And the leftward “blue wave” and its rightward counter in 2018 were a stark continuation of the long-term trend.

Consider where we were just a few years ago.