A top political handicapper shifted its rating on Monday in the pivotal Pennsylvania Senate race, signaling dwindling chances for Democratic Sen. Bob Casey's re-election.

The Cook Political Report shifted the Pennsylvania Senate race between Democratic Senator Bob Casey and Republican Dave McCormick toward Republicans on Monday, just over two weeks before Election Day.

The heated Senate race in battleground Pennsylvania has tightened even further between Sen. Bob Casey (D-PA) and Republican challenger David McCormick as voters already start to cast their ballots. The neck-and-neck contest is one of several that could be the Senate majority-maker by determining whether Democrats hold on to the chamber with a razor-thin margin.