The Campaign for Primary Accountability, a super-PAC solely dedicated to defeating longtime incumbents of both parties, will spend hundreds of thousands of dollars against Reps. Tim Murphy (R-Pa.) and Tim Holden (D-Pa.).

Both are facing tough primary challenges from candidates running as ideological purists: Murphy is facing Tea Party candidate Evan Feinberg while Holden, a centrist Blue Dog Democrat, is facing Matt Cartwright (D), who is running as the more liberal candidate in a revamped district that has been made considerably more liberal.

The group plans to spend approximately $200,000 on each race, about what they've spent on past races against Reps. Jean Schmidt (R-Ohio) and Don Manzullo (R-Illinois), who lost, and Marcy Kaptur (D-Ohio), who won. The group also spent more than $300,000 combined trying to take out Alabama Republican Reps. Spencer Bachus and Jo Bonner, both of whom won their primaries.

While the Manzullo and Kaptur primaries were races against other incumbents, a group spokesman said it would not get involved in the member-on-member race between Reps. Jason Altmire (D-Pa.) and Mark Critz (D-Pa.), or any other primaries in Pennsylvania.

"Our general criteria which have some bearing on this are the length of incumbency," said group spokesman Curtis Ellis. "The voting record only figures in as far as our polling... The key determinant in all of our races is if people are happy with their representative we don't engage, I don't care if they've been there for 50 years."

Pennsylvania's primaries are on April 24.