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.

A small margin in votes separating incumbent Democratic Sen. Bob Casey from Republican challenger David McCormick Jr. has triggered a recount in the Pennsylvania Senate race, the commonwealth's secretary said Wednesday.

Pennsylvania’s Senate race is heading towards a recount between Republican Dave McCormick and Democratic Sen. Bob Casey. NBC News’ Mark Murray reports.

The unofficial results in the race for the U.S. Senate seat in Pennsylvania have triggered a legally required statewide recount, Commonwealth Secretary Al Schmidt said on Wednesday. Democratic Senator Bob Casey and Republican Dave McCormick have vote totals within the one-half of 1 percent margin that triggers a mandatory recount under state law,

The incredibly tight Pennsylvania race between Democratic Sen. Bob Casey and Republican challenger Dave McCormick will head to a recount, Pennsylvania Secretary of the Commonwealth Al Schmidt announced Wednesday.

The U.S. Senate election in Pennsylvania between Democratic incumbent Sen. Bob Casey and Republican David McCormick is headed for a statewide recount, as counties continued Wednesday to sort through outstanding ballots and the campaigns jousted over which ones should count.

The U.S. Senate race in Pennsylvania will now go to a recount, Secretary of the Commonwealth Al Schmidt has announced.