I guess that is pretty close, though the way I see it, 15 to 20 is a difference of 25% or 33%. No matter. More important, I don’t honestly believe that it is possible for anyone to get to the absolute base. Some actions that make someone mad will make others happy. If the “Strong Support” gets down to the 22-25% area, I can not IMAGINE that it can get any lower in a poll- if only because “support” people say “Strongly Support” just because they are feeling sorry for the polled person.
There is not much further to go before “Strong Support” hits rock bottom, in this way of thinking. Again, that is largely because of the solid “base” of “demographic support”(blacks- who I AGREE with ANY reasons they might give, and sympathize with them) who Dear Leader can NOT lose no matter what he does - a support base that no other president in history really enjoyed.
The people O has turned off are those hated "independents" and "conservative Democrats" and Ron Paulists who hated Bush and who voted (ahem) for "change." Once they get to the point that they hate O, it will be "a pox on your house" for all the Dems.