There was a big brouhaha over this report that said Thompson really didn't care if he was President and hates the campaigning process. He was misquoted though about wanting to be Preznit and went on to FNS to explain why he isn't consumed with politics, but you know, even in trying to defend himself, he lacks that "fire in the belly."
And about his drop in the polls---well, you just have to look at the right poll on Real Clear Politics I guess...(h/t Heather)