Dave McCormick defeats Bob Casey in Pa. Senate race

Republican businessman David McCormick has won an upset in Pennsylvania's U.S. Senate race against Democratic incumbent Bob Casey, The Associated Press announced Thursday.

But Casey, a scion of Pennsylvania politics, remained defiant and refused to concede as votes are still being tallied, according to a campaign spokeswoman.

The AP declared McCormick the winner at 4:09 p.m.

McCormick, 59 of Pittsburgh, prevailed in his second run for Senate and will hold his first elected office.

The loss marks the first statewide general election loss for Casey, a three-term incumbent, after polling favored him to win. He has held public office in Pennsylvania since 1997.

With over 97% of the estimated vote in as of Thursday, McCormick had a lead of about 32,000 votes over Casey.

There are still some in-person precincts to be counted across the state, but largely in Republican-rich Cambria County.

Overseas, military, and provisional ballots also still need to be counted.

Casey is not giving up, according to Maddy McDaniel, a campaign spokeswoman.

"As the Pennsylvania Secretary of State said this afternoon, there are tens of thousands of ballots across the Commonwealth still to count, which includes provisional ballots, military and overseas ballots, and mail ballots. This race is within half a point and cannot be called while the votes of thousands of Pennsylvanians are still being counted," McDaniel said in a statement. "We will make sure every Pennsylvanian's voice is heard."

The upset boosts Republicans' hold on the Senate, giving them 53 of the 100 seats in the chamber.

Senate races in Nevada, Arizona, and Maine have not been called.

McCormick, a Washington County native who was raised in Bloomsburg, Columbia County, sought throughout his campaign to paint Casey as a career politician who was out of touch with everyday Pennsylvanians, and he touted his experience in the Army and running large companies.

Casey, 64, of Scranton, is the son of former Pennsylvania Gov. Bob Casey Sr. If he loses, it will be the first time Casey has lost a statewide general election race in a 28-year political career. He was first elected to the Senate in 2007 after serving as the state's treasurer and auditor general.