Did the Supreme Court’s Decision in Citizens United Help Liberal/Progressive Causes in the 2012 Election Cycle?

That possibility is discussed in this article by Molly Ball. The idea is that the Supreme Court's decision in the Citizens United case unshackled the unions not only to spend, but to electioneer beyond its members to the public at large. (The article emphasizes that although unions did whatever they could to take advantage of Citizens United, political directors of key labor Super PACs dislike the decision and would love to see it overruled.)