FILE - In this Oct. 4, 2013 file photo, Rep. John Dingell, D-Mich. is seen on Capitol Hill in Washington. According to AP source: Dingell, the longest-serving member of Congress, to retire.  (AP Photo/J. Scott Applewhite, File)

FILE - In this Oct. 4, 2013 file photo, Rep. John Dingell, D-Mich. is seen on Capitol Hill in Washington. According to AP source: Dingell, the longest-serving member of Congress, to retire. (AP Photo/J. Scott Applewhite, File)