WaPo:

Reps. Donna F. Edwards and Chris Van Hollen clashed Tuesday over the role of super PACs in their hard-fought Democratic primary race for a rare open Senate seat in Maryland.

At a debate televised by WJLA (Channel 7), Van Hollen attacked Edwards for refusing last summer to sign a pledge barring super PAC involvement in the contest and again urged her to sign it — even though outside groups made possible by the Supreme Court’s 2010 Citizens United decision have spent heavily on behalf of both candidate