https://fivethirtyeight.com/features/final-2020-presidential-election-forecast

Anons,

I think all of their polls, which are wrong, are wrong because they a based on some people who voted for Trump in 2016 changing to Biden; and Biden won't lose any Hillary votes because he is likeable.

That is their basis.

In other words, given everything going on in the country — and Biden’s popularity relative to Clinton — it simply shouldn’t be that hard to imagine a small number of voters switching from Trump to Biden. Indeed, that’s what polls show: There are more Trump-to-Biden voters than Clinton-to-Trump voters. The lion’s share of people who voted for Gary Johnson or another third party candidate four years ago also say they plan to vote for Biden.