Republican David McCormick defeated three-term Democratic Sen. Bob Casey in Pennsylvania, the Associated Press projected, underscoring the battleground state’s red shift this year while expanding the GOP’s Senate majority in the next Congress.

Republican David McCormick cut into Democratic Sen. Bob Casey's support in Philadelphia and its populous suburbs and built leads in the more GOP-leaning parts of the state, foreclosing the incumbent's pathway to victory when The Associated Press called the race Thursday.