In it, but not of it. TPM DC
The letter, written by Sen. Michael Bennet (D-CO), will be sent to Majority Leader Harry Reid.
The signatories so far: Sens. Bernie Sanders (VT), Al Franken (MN), Patrick Leahy (VT), John Kerry (MA), Sheldon Whitehouse (RI), Michael Bennet (CO), Sherrod Brown (OH), Kirsten Gillibrand (NY), Jeff Merkley (OR), Dianne Feinstein (CA), Roland Burris (IL), Barbara Boxer (CA), Jack Reed (RI), Tom Udall (NM), Barbara Mikulski (MD) and Frank Lautenberg (NJ).
(H/T Greg Sargent)