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Why Pennsylvania will decide the next president

by Alexander Bolton - 10/10/24 6:00 AM ET

Pollsters and political analysts say Pennsylvania more than any other state will decide the winner of the 2024 presidential election as a new Decision Desk HQ analysis gives the winner of the Keystone State an 85 percent chance of becoming president.

Vice President Harris and former President Trump are pouring more of their time and money into the state than any other battleground, reflecting its sky-high importance to winning at least 270 electoral votes, the magic number needed for victory on Election Day.

Harris and Trump conceivably have other pathways to winning the White House if they fail to carry Pennsylvania, but those alternate scenarios would entail winning states where they are now viewed as underdogs.

“We do not project either candidate reaching 270 electoral votes without winning Pennsylvania, which is currently a dead tie,” The Hill’s Decision Desk HQ reported in a recent forecast and analysis of polling averages.

Scott Tranter, the director of data science at Decision Desk HQ, wrote in a memo that “whoever wins PA has an [approximately] 85% chance of being the next president” and gave Harris a 52 percent chance of winning Pennsylvania and the presidency.

Tranter says Pennsylvania is the decisive state because of its political makeup, which is evenly split between Republican-leaning and Democratic-leaning voters distributed across urban, suburban and rural areas.

He also cited its size, accounting for 19 electoral votes, and its history of voting the same way as two other key Midwestern battlegrounds: Michigan and Wisconsin.

“Generally speaking, and this is what the model looks at, however Pennsylvania goes, Michigan and Wisconsin follow. That’s not always the case, but the model says probabilistically [it happens] more often than not,” Tranter said.

Given Michigan’s and Wisconsin’s history of voting in alignment with Pennsylvania, and its history of voting for Democrats in recent election cycles, pollsters and statisticians say it’s unlikely that Trump would lose Pennsylvania but manage to win either Michigan or Wisconsin.

If Trump won Michigan or Wisconsin, however, and held on to Arizona, Georgia and North Carolina, where he is leading in the polls, he would have enough electoral votes to win back the White House.

Since 1972, when Richard Nixon carried Pennsylvania, the Keystone State has voted for the winner of the presidency in all but two elections — in 2000, when Vice President Al Gore carried the state, and in 2004, when Sen. John Kerry (D-Mass.) won it.

Over that span of 50 years, Michigan, Pennsylvania and Wisconsin have voted the same way in every presidential election except two.

The first exception happened in 1976, when Jimmy Carter won Pennsylvania and Wisconsin but then-President Ford won his home state of Michigan.

The second came in 1988, when Vice President George H.W. Bush won Michigan and Pennsylvania, while Massachusetts Gov. Mike Dukakis (D) won Wisconsin.

Decision Desk HQ’s model factored in demographics, fundraising, polling, incumbency and historic voting patterns among the 500 variables it used to calculate the probable outcome.

“The model runs, in our case, 14,000,605 simulations of how the whole election will go, and in 85 percent of the scenarios, the winner also wins Pennsylvania,” Tranter said.

“It’s a battleground state in the sense that Republicans and Democrats are pretty evenly divided and independents that go back and forth. It’s got a large amount of electoral votes and it correlates highly with other states like Wisconsin and Michigan,” he explained.

He cited the similarities in levels of education and income levels among the states population and similar ethnic breakdowns among voters in the three states.

Decision Desk HQ has Harris and Trump tied in assessed probability to win Pennsylvania, though Harris has a 1-point lead in the state’s polling average.

“Harris’s inability to improve in the polls was particularly cemented by an early October poll showing Trump ahead by 4 points in the state — the highest lead for either candidate in almost a month,” its analysis noted.

Harris maintains a slight probabilistic advantage over Trump in Michigan and Wisconsin but has lost some ground recently in those states’ polling averages.

Harris’s base in eastern Pennsylvania is anchored by heavily Democratic Philadelphia and its surrounding suburbs, which have an affiliation with liberal Northeastern and mid-Atlantic states such as New York, New Jersey and Maryland.

Trump’s base is in the rural parts of the state, which are spread over 54 counties.

Biden, by comparison, won only 13 of Pennsylvania’s 67 counties in 2020, but they accounted for a larger share of the state’s population.

David Paleologos, the director of the Political Research Center at Suffolk University, said Harris needs to win Pennsylvania to win the White House.

“At least according to the data we have now, it looks like Harris is slightly ahead in Wisconsin and Michigan, but she still needs Pennsylvania, because Arizona — at least according to our poll — was kind of tracking away from Harris, and now it seems like Georgia and North Carolina are. And Nevada doesn’t have enough electoral votes to be a tipping point,” he said.

“I think Pennsylvania is really ground zero,” he said.

If Harris loses Pennsylvania, then she would need to win either North Carolina, which has 16 electoral votes, or Georgia, which also has 16 electoral votes, to make up for it. But she’s viewed by pollsters as less likely to win those states.

Decision Desk HQ notes that Harris has trailed Trump in the polling averages of North Carolina and Georgia. It gives her only a 40-percent chance of winning either state.

Trump carried North Carolina in 2016 and 2020. He won Georgia in 2016 but lost it by a mere 11,000 votes in 2020.

J.J. Abbott, a Democratic strategist based in Pennsylvania, said there’s growing consensus that the Keystone State will decide the winner of the presidential election.

“Part of the reason is we’re the largest of the battleground states so it has a significant number of electoral votes to make up [for] if you don’t win it,” he said.

“We’ve seen it throughout the last six months or so,” Abbott said. “Pennsylvania was the first state they really started spending in, it’s the state we’re seeing the candidates be the most active and in a lot of ways it’s a state that takes the most work, because it is so big.

“It’s really diverse, both geographically and demographically. You have to run complex, layered campaigns to be able to reach and talk to all types of voters,” he continued.

Harris announced her running mate, Minnesota Gov. Tim Walz (D), at an event in Philadelphia and spent five days in Pittsburgh preparing for her only debate against Trump, which was also held in Philadelphia.

Harris laid out her economic agenda in Pittsburgh, which is in the heart of crucial Allegheny County, where strategists say she needs to do well to win the broader state.

Trump has held more rallies in Pennsylvania than any other state and has spent more of his advertising budget there than in any other battleground.

Democrats and Republicans have spent $350 million in advertising in Pennsylvania, more than double the $142 million they spent in the next-most contested battleground, Michigan, according to AdImpact data reported by The New York Times.

Biden won Pennsylvania in 2020 after he carried Pittsburgh’s Allegheny County with 59.6 percent of the vote. Hillary Clinton lost the state in 2016 after carrying Allegheny County with 56.4 percent of the vote.

Biden also did better than Clinton in the suburban counties outside Philadelphia — Bucks, Montgomery and Chester counties — which he won with 51.7 percent, 62.6 percent and 58 percent, respectively. Clinton carried those same counties with 48.4 percent, 58.7 percent and 52.6 percent.

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Abbott said Harris needs to “run up the score” in Democratic urban and suburban areas to make up for Trump’s strength in rural parts of the state.

He said Trump has a “loyal base” and “the assumption is that base is going to stick with him and turn out for him.”

“The Harris campaign isn’t taking any votes for granted. They have really strong programs that are focused more on their base voters and out there trying to persuade voters in the suburbs and more independent-leaning areas and also rural areas,” he said.