It doesn't work that way. In fact, Republicans nearly always narrow the gap or increase their lead as elections approach.
The last 3 presidential elections Democrats won they won the popular vote by 4 points or more(7 points in 2008 and 4 points in 2012 and 2020),that along with Gore and Hillary's losses while winning the popular vote by less than 4 points I think it is and will stay correlated. State by state Harris is winning in the polling,but her lead is just 14 electoral votes,Biden's was 100 in 2020 and Trump outperformed the state polling by 27 electoral votes in 2020. In 2016 betting odds had Hillary around 80-90 %,while national polling had her up by 3.2,less than the 4 points or more Obama needed to win in 2008 and 2012 and state polling had her up by 6 electoral votes,for that reason I trust polls more than I do PredictIt.
2016 was a different era. That's the equivalent money markets don't go below $1. I don't have an answer for Trump outperforming in 2020. If I recall, the polls missed Florida big. I will think about what you are saying.
Again, you seem to forget that in swing states Hillary's polling collapsed after the Comey letter, using October polling right after Grab Pussy tape came out isn't the right context to check polls.