Worth noting that most of 538's 'secret sauce' was in combining state by state poll results with national polls to take account of the weird Electoral College system. I'm guessing most of the predictions that people remember as saying Clinton can't lose were basically just predicting the popular vote, which she didn't lose, but even then wasn't really that far outside the margin of error.

https://en.wikipedia.org/wiki/Nationwide_opinion_polling_for...