Well, it really depends on whether you're talking an esoteric objective level of disapproval, or versus another candidate, because the latter is the only one that matters. Against any other non-Black candidate, the Black vote will always be 95% in his corner, as well as the 10-15% or so of Whites who are afraid to be called 'Racist' if they don't visibly worship St. BHO and are hopelessly committed to the Magic Negro hypothesis; it is just about statistically impossible for him to ever drop much below 30%, say a bottom of 25%, by that latter measure.