It's not so much that they prefer Biden over Trump. But they dislike Trump. I know people who cannot stand his antics on Twitter or the way he disrespects women or his blatant infidelity to his wives. However they strongly believe in conservative and Christian values and will hold their nose while the vote for him to try to ensure the supreme court votes their way on issues such as abortion. Trump knows this and uses it as a carrot to encourage these people to vote for him.
Yes, there are lots of people who will tell you how much they dislike Trump, then vote for him. I'm saying that those people still exist even if the Supreme Court spot isn't at stake: a Republican White House still gives them a better chance of legislation upholding conservative values in the future.
