I came here to say exactly the same thing. Silver and 538 are explicit about not doing this. Their models do include the uncertainty of future events, and do

I came here to say exactly the same thing. Silver and 538 are explicit about not doing this. Their models do include the uncertainty of future events, and do adjust closer to 50/50 given the same polls the further from the election it is. That's why Biden's odds have been ticking upwards slightly over the past couple weeks despite polls remaining pretty stable. So in theory, the forecast should be exactly what it appears: the percentage of the time the candidate would be expected to win given the situation they are in at the time of the forecast. So if on Oct. 14 it gives Biden a 72% chance, it means that a candidate in Biden's position, with his polling numbers, and the economic conditions and everything else that is the case on Oct. 14, would go on to win from there 72% of the time. I agree that it appears the volatility of the 2016 forecast was larger than you would expect given a correct model behaving that way. I expect that uncertainty is better expressed in the 2020 model. However it's certainly conceivable for such a model to swing correctly. IE, there's nothing impossible about a candidate having a 90% chance of winning on X date, then having circumstances change such that they only have a 50% chance at Y date. (In fact, if you ignore the discontinuity on election day, at least 10% of the time their odds would have to pass through 50% at some point, as they would go on to lose. And of course there would also be scenarios when it would dip to that level or below and yet still win.)