One of my favorite facts about campaign finance, which illustrates both the fecklessness of the Federal Election Commission and the free-for-all of the current terrain, is that the FEC has not issued one single rule on Super PACs. Ever. Spending by outside groups has quadrupled since the 2006 election, and Super PACs are leading the way in a post-–Citizens United world of unrestrained corporate donations—and yet the government body charged with electoral fairness hasn’t had a thing to say about it. (You might actually call this one of my least favorite facts about campaign finance).

Progressive groups have already forced the White House to explain why it hasn’t forced new members onto the FEC, which could break the current stalemate and force some action on Super PACS and other vehicles for campaign finance. (That explanation is forthcoming; the groups mounted a successful petition drive on the White House online outreach page).

Now, Senate Democrats are adding pressure on the FEC. On Tuesday, ten Democrats plus Bernie Sanders, an independent, sent the FEC a letter urging it to enact broad disclosure rules for Super PACs, and to force more disclaimers on advertisements about who is funding them.

“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.”

The letter was signed by Senators Jeanne Shaheen (NH), Al Franken (MN), Jeff Merkley (OR), Tom Udall (NM), Sherrod Brown (OH), Michael Bennet (CO), Chuck Schumer (NY), Sheldon Whitehouse (RI), Barbara Boxer (CA), Kirsten Gillibrand (NY) and Sanders.

Seven of those senators sent a letter last week to the Internal Revenue Service, asking to investigate—or admit that it is already investigating—the political activities of tax-exempt 501(C)(4) groups. These nonprofits are forbidden from engaging predominantly in “electioneering” activities, and it’s hard to see how groups like Karl Rove’s Crossroads GPS isn’t doing exactly that.

This is important pressure coming from the Hill onto the FEC—and if the White House is serious about campaign finance reform, as it claimed to be last month when announcing that administration officials would support a Democratic Super PAC, then it should join the calls by these Senators for more disclosure and tighter rules.

While we’re on the subject, Stephen Colbert had a delicious roasting of the administration for doing a 180 on Super PACs last night: