It seems to me that these polls are very pro-Trump and pro-Sanders.
Well, they are internet polls. Trump and Sanders could soil themselves on the debate stage and the internet polls would still say they won it in a landslide. Let's not forget they nearly unanimously said Trump/Sanders won the most recent debates easily, but the actual voters thought much differently.
Granted, YouGov at least has the methodology of a scientific pollster, but it's not surprising the "internet poll bias" still creeps in to an extent.