That increasingly becomes the case, which is why most people who are decent at making the predictions weigh the past behaviors and current situation and adjust them as time goes on.
Saying Trump was still favored back in say May could hold a lot of weight. While the current situation was very grim for him, historically candidates in his position won, and a lot could change.
Now we are in the home stretch, less than 3 weeks. Each day that passes Trump's window to change the direction of the election closes, and the current situation dictates what will happen more than historical data.
Basically, if the election were held on any given day since mid April, Trump would have been crushed, and eventually any given day becomes election day if he doesn't change what each day brings.