(AP Photo/Matt Rourke)

Sen. Bob Casey (D) has beaten back a challenge from Republican Tom Smith in Pennsylvania.

Smith appeared to have an outside chance at pulling an upset here. Although Casey always led in polls, the senator found himself in a closer-than-expected race and was outspent by the wealthy self-funder Smith. (The former coal-mining magnate poured about $17 million into the race.) But Casey responded, and he got help from a Democratic super PAC.