Poll Jump

How is it possible that a candidate with a popularity rating in the mid-twenties can jump in a week to the high forties? Hillary Clinton did that, and without any kind of defining moment that I can see, so how did it happen? Who commissioned this poll? Who performed it? Were the participants pre-screened? It's a lousy question, but I don't know of any other way these numbers could be as they are being presented. A twenty point plus is statistically unlikely. I don't believe that being a bad guest at a progressive (although extremely accommodating) convention explains the enormous rise. If this is a fix, it isn't a smart one, far too obvious. Is there a way to verify these results? As they stand, they don't make sense.