The personality was Richard Spencer. His tweet Sunday:
"I plan to vote for Biden and a straight democratic ticket. It's not
based on 'accelerationism' or anything like that; the liberals are
clearly more competent people."
Biden's campaign almost immediately responded to that tweet with:
"When Joe Biden says we are in a battle for the soul of our nation
against vile forces of hate who have come crawling out from under
rocks, you are the epitome of what he means. What you
stand for is absolutely repugnant. Your support is 10,000% percent
This Spencer character has been in the news several times. After Trump took office, he shouted "hail Trump" and people present gave Nazi salutes. He was also scheduled to speak at the Charlottesville counter-rally that ended with the death of a protester in favor of removing Confederate monuments. Spencer called for "peaceful ethnic cleansing."
I see no record of Trump's campaign ever rejecting Spencer's support.