Casey, the incumbent Democrat, has not conceded to his GOP opponent, who was leading Friday morning by a slim margin of only 30,000 votes.

After days of the race being too close to call, the Associated Press named Republican Dave McCormick the winner in the race for one of Pennsylvania’s two seats in the U.S. Senate, defeating incumbent Democrat Bob Casey. McCormick first addressed supporters at his election night party in Pittsburgh when the race was too close to call.

Republican Dave McCormick appeared to win a major upset in Pennsylvania, beating three-term incumbent Bob Casey. The victory would give the GOP a key win in the U.S. Senate, where it now holds 53 seats.