Right, but the job of 538 is exactly to deal with that, and they do take into account the fact that errors are correlated, so if one poll is off, chances are th

Right, but the job of 538 is exactly to deal with that, and they do take into account the fact that errors are correlated, so if one poll is off, chances are they all are. That's why their predictions are fairly conservative. They gave Florida a 1/3 chance for Trump and 1/10 for the presidency. Both those numbers make sense. Now you can argue that there's little utility if the error bars are so big, and you may have a point. The bigger issue here is that modern elections have been extremely close, and unfortunately we cannot get polling accurate enough.