I don't doubt he's ill. Nor did i doubt that Bush jr. was ill in a different way. But i doubt anyone will try to disqualify him on such a point at this time. Rich people are allowed to be crazy as long as their heirs aren't afraid of losing their inheritance. And to challenge his mental well being would be to challenge the mental capacity of his supporters. And that would be a can of worms messier than Obama or anyone else would want to open.
Pretty soon Obama is an opposition party member, don't sweat the past perhaps.