In a stunning upset, GOP challenger David McCormick has unseated three-term Democratic Sen. Bob Casey in Pennsylvania’s Senate race, according to the Associated Press.

Both campaigns expressed confidence in victory on Thursday.

"The count in Pennsylvania is still continuing. Yesterday, the vote margin shrunk by 50,000 votes and this race is now within half a point, the threshold for automatic recounts in Pennsylvania," Maddy McDaniel, spokesperson for Bob Casey for Senate, said in a statement Thursday morning. "With tens of thousands more votes to be counted, we are committed to ensuring every Pennsylvanian's vote is heard and confident that at the end of that process, Senator Casey will be reelected."

The McCormick campaign disagreed.

"McCormick is up 30,679 votes with more to come, as ruby red Cambria County is still outstanding," Elizabeth Gregory, McCormick's communications director, said in a statement earlier this afternoon. "While votes continue to be counted, any way you slice it, Dave McCormick will be the next United States Senator from Pennsylvania."

McCormick's victory is a huge victory for the Republican Party. McCormick has been the underdog in this race the entire campaign and has never been ahead in the RealClearPolitics average. However, signs that Casey was headed for defeat have been showing for weeks.

Last month, the Casey campaign ran an ad that positioned Casey as a moderate. When the ad first came out, I wrote:

The ad emphasizes that Casey “bucked Biden” on fracking, a critical issue in Pennsylvania, and “sided with Trump” on trade policies, particularly in ending NAFTA and imposing tariffs on China. Kamala Harris? She doesn’t even come up, even when Marygrace mentioned “corporate greedflation and price gouging.”

If this ad told us anything, it’s that Casey is trying to distance himself from Biden and Harris while appealing to Pennsylvania’s swing voters by aligning himself with Trump. Casey recognizes Trump’s growing influence in Pennsylvania and sees that he needs to appeal to Trump’s base to secure his reelection.

It looks like it wasn't enough to convince Pennsylvania voters. 

I also wrote, "Casey's record is also not one of an independent voice in Congress; he voted with Biden 99% of the time."

This ad is BONKERS. Bob Casey votes with Biden like 99% of the time. pic.twitter.com/ABLjVnvQcb

— Steve Guest (@SteveGuest) October 18, 2024

Flipping this Pennsylvania seat was especially satisfying for Republicans, given the party’s missed opportunities in other key states like Nevada, Michigan, and Wisconsin. McCormick’s win now provides Republicans with a significant boost, securing a 53-seat majority in the Senate and strengthening the party’s hand as it moves into the 2025 legislative session. Now, attention turns to Arizona, the only remaining undecided Senate race, where Republican Kari Lake trails Democrat Ruben Gallego by two points with 74% of votes reported. 

McCormick had previously campaigned for the Senate in 2022, coming within a hair of clinching the Republican nomination before narrowly losing to Dr. Mehmet Oz. Oz, in turn, faced defeat against Democrat John Fetterman in the general election. As it stands, McCormick’s victory marks a critical gain and a decisive moment for the GOP in a politically volatile election cycle.