Before this came out I was looking at a graph of Democratic candidate's polling figures. It showed Bernie trending sharply up and Hillary trending sharply down. You could see that if current trends continue Bernie will be polling better than Hillary by October/November.
I think that perception of candidates is based on what we know of their history, their stated policies and their charisma.
Bernie's stated policies have been consistently progressive over a long period of time. Hillary's haven't. Bernie has also been willing to take positions on controversial issues. Hillary is less willing to do so.
Bernie takes positions that appeal to the 99%. Hillary is less willing to offend her donors.
In terms of charisma, I don't think there's a clear winner.
Another factor in how candidates are judged is how the media treats them. Until now Clinton has been the clear winner in terms of media coverage, but if Bernie continues getting impressive attendance at rallies and keeps rising in the polls that may change.
All things considered, it seems to me that Bernie's upward trending is going to continue. He's going to force Hillary to mouth support for positions that will offend the donor class - so she's probably going to be reassuring them privately that she's just pulling an Obama on the electorate and wouldn't govern based on her campaign platform.
I'm wondering how Hillary, the DNC and the 1% are going to try to take Bernie down. He's not a candidate they can live with.