He retired before 2008, so Obama doesn't count. He worked for one of Clinton's primary opponents back when Clinton himself was a dark horse candidate, and he actually resigned from Carter's 1976 campaign after ten days, writing to the future President, "I am not sure what you believe in, other than yourself." So it basically boils down to, "he never worked for Jimmy Carter or Bill Clinton".

You could tell a similar story for any Democratic strategist with an overlapping career. Tad Devine worked for the failed campaigns of Mondale 84, Dukakis 88, Kerrey 92, Gore 00, Kerry 04, and Sanders 16. (He also worked in Ukraine on Viktor Yanukovych's winning 2010 Presidential campaign, alongside Paul Manafort. Small world.)

Also, if you work for a successful Presidential election campaign, you end up working in the White House, e.g. George Stephenapolous, Karl Rove, David Plouffe, David Axelrod, and Steve Bannon.