Link, please?
I said it was a rumor. It was posted on FR before and it was poo-pooed as a rumor and rightly so.
I have seen this rumor online three times. While I find it very difficult to believe, here are your links. I agree that if it is true, it completely changes things.
http://blog.washingtonpost.com/thefix/2007/03/the_case_for_fred_thompson.html
Scroll down for the words: Thompson has a skeleton in his closet. Their have been persistent rumors ...
http://blog.washingtonpost.com/earlywarning/2007/03/hagel_vs_obama_what_a_dream.html
Scroll down for: Jack, I don't see it happening for Fred Thompson....
http://www.dailykos.com/story/2007/3/26/163430/711
Scroll down for: will fred thompson answer the question if ...
Hope this helps.