Sanders outperforms the polls again in WI

Sanders won WI 56.5 to 43.2, a margin of 13.3. The last polls before the primary had him up 8 points and 538 said he'd likely win by 2 point. So once again he did better than both the polls and 538 predictions. He'll have to keep this up in order to win the nomination. And it makes me wonder not only what's wrong with the polling and 538, but perhaps how their own biases are trying to influence this election, consciously or not.