Urban areas such as Philadelphia have become exclusively Democratic strongholds while Republicans have “totally taken control of rural, large swaths of the real geography of the state where Democrats at one time actually were competitive. That has left the spaces between as the ultimate arbiters of power in Harrisburg.

“The real battle is over the suburbs and how they’ve shifted,” Kennedy said. “And that’s really where the Democrats have carved out their majority over the last few years in the legislature.”

Ultimately, control of both chambers will likely hinge on fewer than two dozen races across the state, including several in suburban Philadelphia and southeastern Pennsylvania.

Many of the seats in question share a defining characteristic: Voters regularly split their tickets. Some Republican-held districts supported Democratic statewide candidates in recent elections. Others continue electing Democratic legislators even after voting comfortably for Donald Trump in the 2024 presidential election.

Senate Republicans play defense in key Pa. districts

While Republicans begin the election cycle with a four-seat advantage in the Senate, demographic trends may have created opportunities for Democrats in several districts, particularly in suburban Philadelphia. In Bucks County, for example, Democrats are targeting Sen. Frank Farry in the 6th House District. Farry first won his Senate seat by a comfortable 10,000 votes in 2022, and Republicans still command a voter registration advantage, but Democrats have stemmed that trend during Trump’s first term.

Kennedy said that, even with a voter registration advantage, Republicans are facing a steep challenge as Democrats are simply more motivated to show up to the polls as Trump’s approval rating drops.

“A lot can change in a few months, but certainly when you look at that enthusiasm gap, it is certainly real today,” he said. “And for Republicans in competitive races, whether congressional or legislative races, that’s a real warning sign.”

Another area seat — the 24th District, which includes parts of Berks and Montgomery counties — may be even more vulnerable. The incumbent, Sen. Tracy Pennycuick, won her seat by only a 4-percentage-point margin in 2022, one of the lowest Republican Senate seats on the ballot this year. She now faces Democratic challenger Christopher David Thomas, a teacher and community organizer.

In another Bucks County district, the 16th, Republican Sen. Jarrett Coleman is seeking a second term against Lehigh County Controller Mark Pinsley in a rematch of their 2022 contest. Coleman won that contest by eight percentage points, outside of the five points that would make it a top-tier potential to flip, but it could come into play depending on just how wide the enthusiasm gap proves to be.

Republicans fight back

Still, Yost believes the Senate remains a challenge for Democrats, and Republicans have a chance for at least one of their own pickups.

“It seems like the House is more open to supporting maybe picking up a few Democrats there. The Senate is a heavier lift,” he said. “The way voters are distributed by party that I think makes that tougher. So I think the Senate is a bit more likely to weather these external trends.”

In Lancaster County’s 36th Senate District, Democrat James Malone won a special election last year in a district Donald Trump carried comfortably, likely making it the best chance Republicans have at flipping a seat themselves. Malone currently faces Tom Jones, who served as chairman of the East Donegal Township board of supervisors and a police commissioner for the Susquehanna Regional Police Department.

Yost also said that the Republican choice for their gubernatorial nominee — Stacy Garrity — will also mitigate potential losses.

“Their hope is that she’s able to make this race with Gov. Shapiro much more competitive and, by doing that, the downballot effects will be lessened,” he said.