What makes special elections so special

JOHNSTOWN, PA. — Mark Critz was on top of the world.

Seven years ago this May, Critz — longtime district director for Jack Murtha, the powerful Western Pennsylvania Democratic congressman — had not just won his late boss’ seat in a hard-fought special election. He had held the seat for Democrats, handing then-House Speaker Nancy Pelosi a symbolic victory that she could point to as proof that Democrats were well on their way to expanding their majority that November.