It is difficult to imagine any reason why a poll in August of 2015 is relevant to anything at all.
There are two reasons to vote for HRC: She has a vagina (presumably), and she is a Democrat. Other than that, she is an odious, tainted, unattractive, and unqualified candidate. But neither of the two main reasons will change in the next 15 months, and the combination of the two will GUARANTEE her 45% of the electorate. That is to say, any Republican will have to garner more than 90% of EVERYONE ELSE in order to beat her.
Bernie Sanders' success is nothing more than the accumulation of the ANYBODY BUT HILLARY! Democrats. But those people will fall into line when she is the nominee. No one believes they will come out and vote Republican, or even stay home (which is what disaffected Republicans do).
The interesting thing is how the MSM pretends to be holding her feet to the fire over this email server thing, but none has dared to ask the most obvious question: "What gave you the right to conduct your business outside the official communication network of the State Department?" Or, putting it another way, "Who the **** do you think you are?"