Each party poured in nearly $1 million for advertising, most of it negative. A tea party supporter, Burns disagreed with Critz's camp painting the Republican as an "out-of-touch millionaire" more concerned with tax loopholes for corporations and the rich.
Critz, 48, capitalized on a key endorsement from Murtha's widow, Joyce Murtha, and his ties to his hometown of Johnstown, a Murtha stronghold.
In other races, two former U.S. attorneys angling for House jobs had mixed results in their primaries.
—Thomas Marino secured the GOP nomination in the 10th Congressional District in central Pennsylvania. He'll face two-term Democratic Rep. Chris Carney, who had no primary foe.
—Mary Beth Buchanan fell to attorney Keith Rothfus, who worked for the Department of Homeland Security, for the Republican nomination to take on three-term Rep. Jason Altmire in a district that includes Pittsburgh's northern suburbs. Altmire ran unopposed.