There was a Humphrey Society. I inquired with them, but unfortunately they disbanned a few years ago.
You might try posting your search for him at
www.genealogy.com. This is a popular message board. You can post by surname as well as location. There is a field titled "Jump to". Type the surname in this field and it will take you directly there. It's worth a shot.
I wish rootschat had postings by surnames. When you're searching a surname such as Charles, it sure would be nice if the search results didn't list everyone with the given name of Charles.
I'm from Texas. I don't know how they do things in Arkansas, but I am not aware of voter registration information on line.
Good Luck,
cfuller