PHILADELPHIA — Pennsylvania’s nationally watched U.S. Senate race between Democratic incumbent Bob Casey Jr. and Republican challenger Dave McCormick was still too close to call as of mid-morning on Wednesday,

In the race for Pennsylvania's U.S. Senate seat, challenger and Republican Dave McCormick is leading over Democrat incumbent Bob Casey, but right now the race is too close to call. KDKA-TV's Jennifer Borrasso spent election night at the Casey headquarters and has reaction from Scranton.

Incumbent U.S. Sen. Bob Casey is not ready to give up his seat just yet, even as the margin of votes show the three-term senator trailing behind newcomer GOP candidate David McCormick in his re-election bid.

Senate Republicans are feeling optimistic they’ll expand their majority to 53 seats next year as Sen. Bob Casey (D) is trailing Republican David McCormick in Pennsylvania by more than 50,000 votes with 95 percent of the vote counted.

Republican Dave McCormick holds a narrow lead over Democrat Sen. Bob Casey in the U.S. Senate race in Pennsylvania, with final votes still being counted.

Casey, 64, is a stalwart of the state’s Democratic Party, having won six statewide elections going back to 1996. But the vote count early Wednesday morning were suggesting that could change.

One of Pennsylvania’s two U.S. Senate seats is before voters Tuesday. Incumbent Democrat Bob Casey is vying for a fourth term against republican challenger and businessman Dave McCormick. Let’s start with incumbent Senator Bob Casey.

"Casey was running in a very tough environment for incumbents. ... People are sick of Washington and politics as usual," a political analyst tells Pittsburgh's Action News 4.

McCormick has framed the race as one of strength versus weakness. Casey has worked to make it a question of honesty.

Pennsylvania’s U.S. Senate race between three-term Democratic Sen. Bob Casey and Republican David McCormick will help determine control of the chamber