Gingrich reveals income, but not how he earned it

Republican presidential candidate former, House Speaker Newt Gingrich, seen with his wife Callista at center, campaigns at a Chick-Fil-A in Anderson, S.C., Saturday, Jan. 21, 2012, on South Carolina's Republican primary election day. (AP Photo/Matt Rourke)

January 26, 2012 1:20:52 PM PST
Former House Speaker Newt Gingrich beat his main GOP presidential rival, Mitt Romney, to the punch by releasing his most recent tax return. But Gingrich still hasn't revealed how he earned most of his $3.1 million.