Actually, Quayle isn't stupid. However, he got stuck with a couple of verbal gaffes, and since he didn't have the Goron shield that the press gave Al, those have diminished his reputation, and quite unfairly.
Quayle actually graduated from law school and passed the bar exam, as did his wife Marilyn. They are a couple of nice, brigiht people who were not prepared to deal with the media poison.
Also, he unfortunately had that ace politician Bill Kristol as his chief of staff, which was guaranteed to cause problems.
You don't see Quayle much because he has another quality the Gores lack: dignity.
I have heard Dan speak and he just seems confused. I know he is a nice man and I know he wasn't ready for the spotlight he received.
I also know that algore is not a nice man, really is confused and he also isn't ready for the spotlight.