I can vouch for the truth of what has been said here. Everybody in GA (at least everybody who was old enough to be paying attention) knew the story of how Cleland was injured - he acknowledged it himself. It was only during his last Senate race that the "alternative" stories about Khe Sanh and the supposed Viet Cong (or friendly) grenade began circulating (by Dem operatives, not by Cleland himself), and it didn't wash here because most voters knew the truth. Also, the alternative stories were mutually exclusive - several supposed eyewitnesses who had never said anything before (despite numerous magazine articles, a national photo-essay and a book) suddenly saying (1) it was a VC grenade (2) it was another soldier's grenade (3) it was during a fire fight (4) it was not in a "hot" zone etc. etc.
That said, Cleland was given a pass for years because of his grievous injuries. He was a horrible VA director under Carter, he led what amounted to destruction of the department and it really has never recovered. He was a dreadful senator, very disconnected from his work and simply voted the hard-left Dem party line and was awful as far as constituent response goes (I'm familiar with this personally - his office was notorious for sending out not only mere form letters but the wrong form letters in response to constituent questions and complaints.) I read in Atlanta magazine a number of years ago that he suffered for years from undiagnosed sleep apnea and essentially slept through a lot of his time in office.
That said, everybody was willing to give him a pass until he went on the aggressive attack for the first time during the last Senate campaign and started screaming that his opponent was attacking his patriotism by criticizing his record. As long as he did NOT play the "vote for me - I'm a wounded war veteran" card but let the voters simply infer it, it was a very successful strategy for getting elected. But all free rides come to an end some day, and he depended on that strategy as his one and all. Apparently he never considered that he couldn't mess up constituent services and vote like Ted Kennedy forever . . .
By attacking President Bush, he's just continuing the hard-line attack strategy that lost him the election. Maybe he or Kerry's campaign strategists figure it will play with people who don't know his record, maybe he's just desperate, maybe he just doesn't care any more. I don't know. My personal feeling is that he's still angry and bitter from his loss and doesn't care who gets hurt so long as he can vent.