The Democratic Party is losing its edge over the GOP in the critical swing state of Pennsylvania, with Democrats changing their party affiliation at more than twice the rate of Republicans, according to state data released after voter registration ended Monday evening.

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. 

More than 1.4 million voters are registered as third-party or independent voters in the Keystone State. 

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. 

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Harris Trump photo split

Kamala Harris and Donald Trump (Getty Images)

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.

President Biden won the state in 2020 by 1.17 percentage points​. That year, Democrats had a larger margin of registered voters compared to their Republican counterparts, at 4.2 million to 3.5 million. The data show that Democrats had a registration advantage over Republicans by 685,818 voters during an election Biden won by 80,555 votes.

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 Trump campaign on the ground in Pennsylvania celebrated the data, saying "Kamala Camp HQ is no doubt asking what the heck their 400 paid staffers and 50 offices in Pennsylvania have been doing this whole time, since their only output seems to be drumming up some meaningless stories about office openings and their supposedly well-oiled ground game." 

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More than double the number of previously registered Democrats changed their party affiliation this cycle compared to the number of registered Republicans who left the party: 54,668 registered Democrats changed their party affiliation compared to 25,634 Republicans, Pennsylvania Department of State data shows.

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. 

man at voting booth voting

A voter fills out a mail-in ballot at the Board of Elections office in the Allegheny County Office Building on Nov. 3, 2022, in Pittsburgh. (Jeff Swensen/Getty Images)

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. 

Poor campaign management and staffers lacking relationships with Democratic political leaders in the Keystone State are allegedly rocking the campaign, Politico reported last week. The outlet reported that Democrats are worried that the campaign’s state manager lacks an understanding of Philadelphia, the state’s largest city, while campaign staffers have allegedly not invited local Democratic politicians to events in the state, and have not effectively deployed surrogates. 

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Politico reported that it spoke with 20 Democratic politicians, allies and party leaders for the story and that they were restless over Harris’ campaigning efforts. 

"Our campaign is running the largest and most sophisticated operation in Pennsylvania history," Harris’ national campaign manager Julie Chávez Rodriguez said in comment to Fox News Digital when asked about the report last week. "While Trump’s team still refuses to tell reporters how few staff they have in the state, we have 50 coordinated offices and nearly 400 staff on the ground."

"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."

Kamala Harris closeup shot

Vice President Kamala Harris speaks at a campaign event at Divine Faith Ministries International on Oct. 20, 2024, in Jonesboro, Georgia. (Megan Varner/Getty Images)

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.

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"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."

Bob Casey and Dave Mccormick in photo split

Democratic Sen. Bob Casey and Republican challenger Dave McCormick (Mark Makela/Getty Images)

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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. 

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Pennsylvania is touted as the state that will likely determine the outcome of the general election on Nov. 5. A Fox News survey of Pennsylvania voters published late last month found Harris narrowly ahead of Trump by two points (50-48%) among registered voters, while the race is tied at 49% each among likely voters. 

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

Get the latest updates from the 2024 campaign trail, exclusive interviews and more at our Fox News Digital election hub.