Ask yourself one question.
Do you know anyone who voted for Trump in 2016 who will vote for Biden in 2020?
Thus, if no 2016 Trump voters are voted for Biden in 2020, there is no way that Trump can lose.
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And a lot of people are telling anedotal stories about people they know who voted for HRC who have told them they are voting for Trump. So POTUS should win with a landslide.
Yes I know several people that likely will flip from Trump to Biden as things stand today.