Key battleground state voter registration data shows influential shifts favoring GOP

A total of 9,088,583 registered voters were tallied across the state when the sign-up period ended at midnight on Monday. Registered Democrats maintained a lead over registered Republicans, at 3,971,607 registered Democrats to the GOP's 3,673,783. 

Though the Democratic Party accounts for nearly 44% of registered voters compared to the GOP's 40%, it has seen its advantage over Republicans dwindle this year. 

In 2020, there were 9,090,962 registered voters across the parties in Pennsylvania, only slightly more than the 9,088,583 voters registered this cycle. 

The GOP has whittled down that lead this year to a 297,824 margin. When comparing registered voters this election year to 2020, Democrats face a net loss of 257,281 voters, while Republicans have a net gain of 428,537 registered voters. 

The data is broken down by county, with Philadelphia notably reporting 18,928 Democrats changed their party affiliation compared to just 3,401 Republicans doing the same. Bucks County, which sits outside of the City of Brotherly Love, reported 2,089 Democrats changed their party affiliation compared to 1,624 Republicans. In Allegheny County, home to the state's second-largest city of Pittsburgh, 6,564 Democrats changed their party affiliation while 2,202 Republicans did the same. 

The registered voter data comes after reports surfaced that concerns were mounting within the Democratic Party that the Harris campaign is failing to effectively connect with voters in Pennsylvania. 

"While the Trump campaign closed its 'minority outreach offices,' we invested in targeted advertising to Black and Latino voters starting in August of 2023 and have now spent more than any previous presidential campaign on outreach to these communities. The Vice President is also campaigning aggressively in Pennsylvania - spending 1 out of 3 days in the state in September."

Vulnerable incumbent Democratic Sen. Bob Casey made national headlines last week when he distanced himself from Democratic Party leaders and launched a campaign ad detailing how he "bucked Biden" and "sided" with former President Trump. 

The ad features a married couple - Republican Marygrace and her Democrat husband Joe - praising Casey as an "independent," citing his support for Trump's trade policies and efforts to "protect fracking" from the Biden administration.

"Our marriage - pure bliss! But on politics, we just don't agree. Except for Bob Casey. He's independent," Marygrace says, with her husband chiming in, "That's right!"

"Casey's leading the effort to stop corporate greedflation and price-gouging," Marygrace continues. "Casey bucked Biden to protect fracking and he sided with Trump to end NAFTA and put tariffs on China to stop them from cheating. So in this house, we agree, it's Bob Casey who's doing right by Pennsylvania."

Casey has served in the Senate since 2007, ultimately becoming a stalwart within the Democratic Party, voting on legislation Biden supported, for example, 98.5% of the time, according to FiveThirtyEight data. He is now facing his toughest re-election effort yet, as he squares up against Republican challenger Dave McCormick. 

The Fox News Power Rankings score the presidential contest in Pennsylvania as a toss-up, with the Senate race a lean Democrat designation. The Cook Political Report, this week, however, shifted the Senate contest from a leans Democrat race to a toss-up race, underscoring Casey's difficult re-election battle. 

Fox News Digital's Chris Pandolofo and Brooke Singman contributed to this report.