My first thought when I saw this was that Obama was not happy about super PACS, but when the republicans had them, he realized from a money perspective he would have to use PACS too.  Then, he announced to the country, he was accepting help from super pacs that supported him (his take was under 100,000..............not too good considering republicans are getting millions in support).  So now, since the democrats aren't getting millions, perhaps this is an attempt to make sure republicans don't either?   Certainly, I am quite sure, if Obama had gotten huge money and support, this move by senate democrats would not even be a consideration :).

The letter comes a day after super PACs reported hauling in tens of millions of dollars in January alone, with much of that cash raised by groups that support GOP presidential candidates and conservative causes.

“While the First Amendment guarantees the right of free speech, we must be sure that the corporate structure does not obscure the speaker,” the senators wrote. “This is why we believe that the identity of individual contributors should also be disclosed when they make substantial donations to organizations financing independent expenditures.”

Signatories included Democratic Sens. Jeanne Shaheen (N.H.), Al Franken (Minn.), Jeff Merkley (Ore.), Tom Udall (N.M.), Sherrod Brown (Ohio), Michael Bennet (Colo.), Chuck Schumer (N.Y.), Sheldon Whitehouse (R.I.), Barbara Boxer (Calif.), Kirsten Gillibrand (NY), and Vermont Independent Sen. Bernie Sanders.

Read more: http://www.politico.com/news/stories/0212/73136.html#ixzz1n77lakMb