Each election about 8% of Republicans vote for the Dem candidate, and 8% of the Democrats vote for the Republican candidate.
That will remain true this year as well. The latest polls are very clear that the Never Trump array on the GOP side is far below 10%. Their voices are amplified by the media, not their numbers.
And bearing in mind that both parties are mere Fringe arrays drawing only 27% each of the electorate, with 47% Independents, the Never Trump fringe of the fringe are even more insignificant.
A recent poll posted here showed that Trump gets 97% of his 2020 voters and Biden loses 20% of his 2020 voters with 10% of those voters now supporting Trump.