This can only help Nader's ratings
Absolutely..
this scandal can only elevate him a notch in the eyes of the dim-base.
If it can be proven true, make it two notches.
I assume he reported the story in the hope that it would reduce Nader's ratings. You are right. I doubt that Nader's support gives a hoot whether he had sex with a dog. Dan Rather making a story of a Nader sex scandal is likely to make a certain portion of the voting public mad, and inevitably draw those votes to Nader.