Critz was Murtha's district director, which I believe means he wasn't based in DC at all, but certainly can be still be tied to Murtha's own personal ethics issues.
This is now the fourth straight race Hafer has quit. In 2005-06, she in turn announced for and dropped out of PA-SEN, PA-18 and PA-Lt-Gov.
The other thing worth noting is that this district will likely disappear in redistricting. We're losing one seat, so why not axe the messed-up-shape district with a diminishing population and the newest incumbent?