- No one voting for Hillary in 2016 is voting for Trump in 2020
- People voting for Gary Johnson or Jill Stein in 2016 are either not voting or voting for Biden in 2020
- Democrats who didn't vote in 2016 out of protest for Bernie Sanders not getting the nomination are either not voting again or they're voting for Biden in 2020
- People who voted for Trump in 2016 fall into three camps: they're either voting for Trump in 2020, voting for Biden in 2020, or not voting at all.
All in all it looks like Biden is going to get more votes than Hillary did in 2016 and Trump is going to get fewer votes than he did in 2016. Trump's incredible campaign gaffe in Minnesota has cost him that swing state and is swinging the rest of the swing states of the U.S. Midwest, which is where I live, to Biden.
Bottom line - Biden's path to the White House appears to be less shaky than Trump's path to the White House. However, Trump has made comments indicating that he's willing to make this election cycle very ugly and we may be looking at our first non-peaceful transition of power in American history.
I'm no political science expert or anything, that's just how things appear to me.