Well, this is a surprise (via Fran Spielman and Carol Marin at the Sun-Times):

Chicago's corruption-fighting Inspector General David Hoffman has resigned to enter the Democratic primary for the U.S. Senate, removing a giant thorn from Mayor Daley's side.

A former federal prosecutor who specialized in breaking up street gangs, Hoffman was hired away from the U.S. attorney's office in 2005 at a time when Daley was besieged by the Hired Truck, city hiring and minority contracting scandals.

Back in June, I told readers to "keep an eye" on a possible bid by Hoffman for higher office.  I also noted that "we have no idea about his personal politics" considering he spent the past decade in the U.S. attorney's office and the IG post.  That stands true today.  But we're obviously going to be learning a lot more in the coming months.

UPDATE (1:00 p.m.): Here's a link to Hoffman's campaign website (H/T Dan O'Neil) and his introductory video (H/T Capitol Fax) is posted below:

Also, Laura Washington gives her thoughts on the new candidate here.