> Where are they? Five different posters have claimed this, but zero have been able to link to the historical predictions.

They are literally charted on the page with the current prediction, e.g., for the 2016 Presidential race (which is locked on the last forecast):

https://projects.fivethirtyeight.com/2016-election-forecast/ , under “How the forecast has changed”, it charts the forecast (by default, the win probability) for the entire time the race was being forecast.