The 2024 United States Senate election in Pennsylvania was held on November 5, 2024, to elect a member of the United States Senate to represent the state of Pennsylvania. Republican businessman Dave McCormick won his first term in office, defeating Democratic three-term incumbent Bob Casey Jr. in what was considered a major upset. Most predictions gave Casey a slight advantage, and he led in most polls. Along with Sherrod Brown in Ohio and Jon Tester in Montana, Casey was one of three incumbent senators to lose re-election in 2024, all of whom were Democrats first elected in 2006.
The primary election took place on April 23, 2024. The election was considered essential for Democrats' chances to retain their majority in 2024. The Associated Press and Fox News declared McCormick the winner on November 7, while Decision Desk HQ called the race for McCormick on November 14. CNN, NBC, ABC, and CBS all called the race for McCormick on November 21; Casey conceded the race later that day, halted a recount and confirmed the result.
This was Pennsylvania's closest US Senate election since the passage of the Seventeenth Amendment, as well as the closest Senate election of the 2024 cycle. McCormick was the only Republican challenger to win in a state flipped by Trump in the 2024 presidential election. The other three Republican Senate gains were in states Trump had won in all three of his runs. With Democrats flipping the other Senate seat two years earlier, this was the first time since the 2012 Senate election in Indiana where the opposite party flipped a seat after losing one in the previous cycle.
This was Casey's first general election loss of his political career, and the second counting Casey's primary election loss in 2002. McCormick was sworn in on January 3, 2025.
Background
Pennsylvania is considered to be a purple state at the federal level, especially since in the 2020 presidential election, Joe Biden carried Pennsylvania by about 1.2 percentage points. Democrats had controlled both U.S. Senate seats, the governorship, a majority of its U.S. House delegation, and the Pennsylvania House of Representatives. The last time Republicans won a U.S. Senate seat in Pennsylvania was in 2016.
Senator Bob Casey Jr. was first elected in the blue wave of 2006, defeating then-incumbent Senator Rick Santorum by about 17 percentage points. He was re-elected in 2012 by 9 percentage points (when he ran ahead of Obama by almost 4 points) and in the blue wave of 2018 by 13 percentage points. Given these three decisive victories, Casey's fourth term appeared inevitable for much of the race. However, tightening polls in the final weeks indicated a closer contest, even as Casey was largely considered the favorite to win.
Democratic primary
Candidates
Nominee
- Bob Casey Jr., incumbent U.S. senator (2007–2025)
Disqualified
- William Parker, app developer
Endorsements
Bob Casey Jr.
Executive officials
- Patrick Murphy, Acting Secretary of the Army (2016), former U.S. representative for PA-8 (2007–2011)
U.S. senators
- John Fetterman, U.S. senator from Pennsylvania (2023–present)
- Mark Kelly, U.S. senator from Arizona (2020–present)
U.S. representatives
- Chris Carney, PA-10 (2007–2011)
- Chris Deluzio, PA-17 (2023–present)
- Chrissy Houlahan, PA-6 (2019–present)
- Conor Lamb, PA-17 (2018–2023)
Statewide officials
- Josh Shapiro, Governor of Pennsylvania (2023–present)
- Gretchen Whitmer, Governor of Michigan (2019-present)
Individuals
- Harry Dunn, former U.S. Capitol Police officer
- Cristina Tzintzún Ramirez, labor organizer and president of NextGen America PAC (2021–present)
Political parties
- Pennsylvania Democratic Party
Organizations
- American Israel Public Affairs Committee (AIPAC)
- CASA in Action
- Council for a Livable World
- Democratic Majority for Israel
- End Citizens United
- Feminist Majority PAC
- Giffords
- Harvard College Democrats
- Human Rights Campaign
- Humane Society Legislative Fund
- Jewish Democratic Council of America
- Joint Action Committee for Political Affairs
- League of Conservation Voters
- National Committee to Preserve Social Security and Medicare
- Natural Resources Defense Council
- NextGen America PAC
- Peace Action
- Pennsylvania State Education Association
- People for the American Way
- Swing Left
Labor unions
- Actors' Equity Association
- AFSCME Council 13
- Association of Flight Attendants
- National Education Association
- Pennsylvania AFL–CIO
- United Mine Workers of America
- United Steelworkers
Newspapers
Republican primary
Candidates
Nominee
- Dave McCormick, former U.S. Under Secretary of the Treasury for International Affairs (2007–2009), former CEO of Bridgewater Associates (2020–2022), and candidate for U.S. Senate in 2022
Withdrawn
- Brandi Tomasetti, former Conestoga Township treasurer and secretary (ran as a write-in candidate)
Disqualified
- Joseph Vodvarka, spring manufacturer and perennial candidate
Declined
- Kathy Barnette, political commentator, nominee for Pennsylvania's 4th congressional district in 2020, and candidate for U.S. Senate in 2022
- Stacy Garrity, Pennsylvania State Treasurer (2021–present) (running for re-election)
- Doug Mastriano, state senator for SD-33 (2019–present) and nominee for Governor of Pennsylvania in 2022 (endorsed McCormick)
Endorsements
Dave McCormick
Executive Branch officials
- George W. Bush, 43rd President of the United States (2001–2009)
- Karl Rove, former White House Deputy Chief of Staff for Policy (2005–2007)
- Donald Trump, 45th President of the United States (2017–2021) and Republican presidential candidate
Federal officials
- John Bolton, former National Security Advisor (2018–2019) and former Ambassador to the United Nations (2005–2006)
- Dina Powell, former Deputy National Security Advisor for Strategy (2017–2018) (his wife)
State cabinet officials
- Robert Gleason, former Pennsylvania Secretary of the Commonwealth (1985–1987)
U.S senators
- Pat Toomey, U.S. senator from Pennsylvania (2011–2023)
- Rick Santorum, U.S. senator from Pennsylvania (1995–2007)
- Marsha Blackburn, U.S. senator from Tennessee (2019–present)
- Steve Daines, U.S. senator from Montana (2015–present)
- Mitch McConnell, U.S. senator from Kentucky (1985–present) and Senate Minority Leader (2007–2015, 2021–2025)
U.S. representatives
- Brian Fitzpatrick, PA-1 (2017–present)
- Jim Jordan, OH-4 (2007–present)
- John Joyce, PA-13 (2019–present)
- Mike Kelly, PA-16 (2011–present)
- Dan Meuser, PA-9 (2019–present)
- Scott Perry, PA-10 (2013–present)
- Guy Reschenthaler, PA-14 (2019–present)
- Lloyd Smucker, PA-11 (2017–present)
- Glenn Thompson, PA-15 (2009–present)
State senators
- Ryan Aument, state senator for SD-36 (2015–2024)
- Doug Mastriano, state senator for SD-33 (2019–present) and 2022 GOP nominee for Governor
Local officials
- Sam DeMarco, at-large Allegheny County councilor (2016–present) and chair of the Allegheny County Republican Party (2018–present)
Party officials
- Andrew Reilly, Republican National Committeeman from Pennsylvania (2020–present)
- Christine Toretti, Republican National Committeewoman from Pennsylvania (1997–2025)
Organizations
- Americans for Prosperity
- Conservative Political Action Conference
- Log Cabin Republicans
- Pennsylvania Federation and Penn State College Republicans
- Republican Jewish Coalition
Political parties
- Pennsylvania Republican Party
Individuals
- Kenneth C. Griffin, businessman
- Paul Tudor Jones, philanthropist
- Matt Schlapp, chair of the American Conservative Union (2014–present)
- Charles R. Schwab, investor
Third parties
Libertarian convention
Nominee
Eliminated at convention
- Erik Gerhardt, carpenter, nominee for U.S. Senate in 2022, and candidate for president in 2020
Green Party
Nominee
Constitution Party
Nominee
- Bernard Selker, truck driver
American Solidarity Party
Disqualified
General election
Post-primary endorsements
Dave McCormick (R)
Polling
Aggregate polls
Results
Results by county
Counties that flipped from Democratic to Republican
- Beaver (largest municipality: Aliquippa)
- Berks (largest municipality: Reading)
- Northampton (largest municipality: Bethlehem)
By congressional district
McCormick won nine of 17 congressional districts, with the remaining eight going to Casey, including one that elected a Republican.
Analysis
In Pennsylvania, a statewide recount is triggered under state law if the margin falls within 0.5% of the total vote. Preliminary results for the election reached this threshold on November 13, 2024, with McCormick at 48.9% leading Casey's 48.6%, as outstanding ballots continued to be counted across the state. Secretary of the Commonwealth Al Schmidt officially ordered the recount later that evening, with Casey declining to concede. The deadline for the counties to begin their recounts is on November 20, the third Wednesday after the election according to state law, however, counties can start their recounts as early as November 18, with all counties required to submit their results to the Department of State by noon on November 26 as the results must be reported by the Secretary of the Commonwealth by noon on November 27. Additionally, the counties must use different machines for the recount than were used on Election Day.
On Monday, November 18, following a series of challenges and disputes, the Pennsylvania Supreme Court directed all of the state's county election officials not to count certain mail-in ballots which arrived on time yet lacked a correct handwritten date on the return envelope.
The last instance of a statewide recount being held was for the 2022 Republican primary for Pennsylvania's Class 3 Senate seat, of which McCormick was also a candidate. Conversely to his stance in the 2024 general election, he unsuccessfully sued to have undated mail-in ballots counted. After completion of the recount he would concede to Mehmet Oz, with the final results expanding Oz's margin by 49 votes.
McCormick benefitted from the presence of former President Donald Trump on the ballot, who carried the state over Vice President Harris by just over 120,000 votes (for a margin of roughly 1.7%) in the concurrent presidential election. Indeed, McCormick cleared 60% in most counties in the state’s less-populated interior and even 70% in many. Unlike in Ohio and Montana, however, McCormick had to seek support beyond the Trump base as he was running in a swing state. Casey and Trump both won Bucks, Erie, and Monroe Counties. McCormick campaigned with Nikki Haley in the suburbs of Pittsburgh and Philadelphia, aiming to appeal to voters uneasy about Trump by positioning himself as a more establishment candidate. Casey aired ads in late October to highlight his votes with the Trump administration, while McCormick tied Casey to Harris, highlighting his votes with the Biden administration.
However, both candidates received fewer votes than their respective parties’ presidential candidates in the concurrent 2024 presidential election. Senator McCormick received about 144,000 fewer votes than President Trump, while Senator Casey received almost 39,000 fewer votes than Vice President Harris. McCormick overperformed Trump's margins in the Philadelphia suburban counties of Chester, Delaware, and Montgomery.