I don't understand your point.
In ranking presidential candidates, most left-or-center-leaning voters would rank any and every Democrat above any and every Republican, with Trump as their very last choice. So the presence or not of any specific candidate doesn't change the outcome. They would have voted in whomever the Democrat Nominee was.
There was lots of reporting in 2020 about Democratic voters who preferred another candidate throwing their support behind Biden based on the idea that he was best positioned to win in the general election.