Since 1948, no Democratic presidential candidate has secured the White House without winning Pennsylvania. Overall, the state has favoured 10 of the past 12 election victors.

Armed with 19 electoral college votes, a fraction of its past tally, Pennsylvania has the largest bounty among the seven swing states. According to the RealClearPolitics polling average, Donald Trump and Kamala Harris are tied in the state. As elections analyst Nate Silver views it, Pennsylvania has a 35% chance of tipping the presidential race.

John Updike, the late writer defined by stories about his native Pennsylvania, once told Life magazine: “I like middles. It is in middles that extremes clash, where ambiguity restlessly rules.” In Pennsylvania, the prevailing electoral mood remains so unclear because of this clash, which is intensified by its demographic complexity when compared to other swing states. Even since 2016, Pennsylvania has experienced profound demographic and economic change — from increasingly Latino-majority cities to booming healthcare-driven suburbs— making that year’s presidential election a fruitless baseline for understanding the state’s present electoral map.

In the case of voter registration, from formerly staunch Democratic regions to suburban Philadelphia, Republicans have added more than 103,000 new voters since January. As a result, Democrats have a 169,000 voter-registration majority compared to the advantage of 559,000 they enjoyed in 2020. This dramatic shift is driven in part by party affiliation lagging behind voting patterns, but also by voters’ economic discontent during Biden’s presidency. According to a recent CBS News poll, 82% of registered Pennsylvania voters ranked the economy as the major factor in their presidential vote. Meanwhile, 7% of state voters rated the condition of the national economy as “very good”.

Both ends of the state could prove measures of this prevailing voter issue. Western Pennsylvania — where the state’s natural gas industry is centred — is home to Pittsburgh’s Allegheny County, among the nation’s biggest population losers based on census numbers. The county has also lost 50,000 jobs over the past five years — more than the state’s 66 other counties. Downtown Pittsburgh, the heart of the region’s eds-and-meds economy, has emptying skyscrapers — a sobering trend for a city defined by its decades-long renaissance. As the Pittsburgh Post-Gazette recently reported, the city’s progressive politics have “ignited […] opposition. Suburbs have grown increasingly Republican in response to the bright blue urban center.”

In eastern Pennsylvania, the populous Lehigh Valley is booming as a centre for warehousing and logistics but also healthcare. In 2023 the sprawling area enjoyed more economic-development projects than any other US region with a population between 200,000 and 1 million. But all this truck-congested growth has led to quality-of-life concerns, and apprehension about the comparatively lower wages associated with warehousing jobs in a state that had the highest grocery inflation rate last year. The region itself has a significant Latino population, which now forms 6% of the statewide electorate. If this voting bloc is mobilised, it could prove increasingly open to the post-Trump GOP.

Though Pennsylvania ranks fifth among states with the most colleges, it’s still a bastion of working-class voters without higher-education degrees. It is this bloc — black voters in Harrisburg, the capital city; Latinos in Reading, the fourth-largest city; formerly Democratic white Catholics in northeastern Pennsylvania; a cross-section of Trump supporters in Philadelphia’s Northeast — that has turned against the Democratic Party. This election will test whether these groups can overcome Democratic-trending suburban growth in formerly GOP communities.

This week, on the question of predicting Pennsylvania’s electoral outcome, journalist Mark Halperin responded: “The answer is ‘don’t know.’” It is this ambiguity, driven by those demographic “middles”, that make Pennsylvania so pivotal in November.