Sen. Tim Johnson (D-S.D.) announced Tuesday that he won't seek reelection, but supporters hope to keep the seat in the family.

A movement was launched Wednesday to draft U.S. attorney Brendan Johnson, the senator's son, into the now-vacant Democratic primary. The effort is being spearheaded by the chairman of the Lincoln County Democratic Party, Ryan Casey.

The basic Web site includes a petition on which people can urge Johnson to run. As of this posting, 11 names appear on the list.

Johnson has been rumored as a potential candidate for the seat for months now, with his father's possible retirement being no secret.

Casey, as it happens, has worked with Johnson's potential primary opponent, former congresswoman Stephanie Herseth Sandlin, at Raven Industries in Sioux Falls, S.D. But the two aren't particularly close, and Herseth Sandlin beat Casey's father, Dick Casey, in a 2004 primary.