Politico reports Illinois Rep. Aaron Schock (IL-18) resigned Tuesday, less than 12 hours after that website raised questions about tens of thousands of dollars in mileage reimbursements he received for his personal vehicle. This is just the latest in a series of ethical questions that have dogged Schock, who recently began his 4th term. The resignation will be effective March 31. 

This vacancy will create the third open seat in Congress, all Republican. Peter Grimm (NY-11) resigned on January 5; a special election is scheduled for May 5. Alan Nunnelee (MS-01) died February 6; a special election will be held May 12. Both these seats are expected to remain in Republican control, as is Schock's seat. Per Roll Call, Illinois Governor Bruce Rauner must call for a special election within 5 days of the effective date of the resignation. The special election must be held within 115 days from the date of that announcement.

Looking ahead to 2016, 7 other Representaives have announced they will not seek re-election. Republicans Chris Gibson (NY-19) and Mike Fitzpatrick (PA-08) are in the most competitive districts; rated toss-up by Sabato's Crystal Ball. Four Democrats in safe districts are leaving: Janice Hahn (CA-44), Donna Edwards (MD-04), Chris Van Hollen (MD-08) and Charles Rangel (NY-13). Reps. Edwards and Van Hollen are running for the Senate seat being vacated by Barbara Mikulski.  Republican Candice Miller (MI-10) is also leaving; her seat is safe for the GOP.