What tragedy about his daughter?
http://en.wikipedia.org/wiki/Fred_Dalton_Thompson
Although he announced in the wake of the September 11, 2001 attacks his intention to seek re-election, upon further reflection, which seems to have been prompted in large part by the sudden death of his daughter (Elizabeth "Betsy" Thompson Panici) on January 30, 2002 from accidental drug overdose[10][12], he decided not to pursue this course.
I'd answer you but cannot deprive you of an opportunity to learn more about FDT. Better that you go here
and click on Biographical Info...
and check out Sturm Ruger's excellent list of links, here:
http://www.freerepublic.com/focus/f-news/1810458/posts?page=27#27
Enjoy! :)