Democratic incumbent Sen. Bob Casey left his election watch party early Tuesday night after polls reported GOP challenger David McCormick in the lead for the U.S. Senate race.

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.

Pennsylvania’s U.S. Senate race between three-term Democratic Sen. Bob Casey and Republican challenger David McCormick will help determine control of the chamber Tuesday in a battleground state contest that is one of the nation’s most expensive this year.

Casey v. McCormick tracks as second-most expensive race in the nation in a year where every seat counts in the battle for majority control of the U.S. Senate.

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

Pennsylvania Sen. Bob Casey is vying for a fourth term against challenger and businessman Dave McCormick in an extremely close race that could ultimately play a role in the balance of power in the United States Senate.

As of early Wednesday morning, 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. While Casey held a lead for much of the campaign,