So according to the forum since Kamala Harris, the second-worst polling Dem candidate (39%) over only Delaney, is virtually certain to beat Trump, I can't wait to see how much the other Dem candidates would beat him by.
The reason why she polls low against Trump is because of her name recognition (duh). Trump polls the same against her as he does for about every other democrat candidate, either 38% or 39%.
That assumes that if she were more known, she would be polling 3-12 points better, while Trump would gain virtually nothing. While that's certainly possible, it's a best case scenario for her. The other candidates besides Delaney all poll better for sure.
The candidates who are already better known also haven't yet become the targets of the GOP attack machine in the way that they would once they win the nomination. If, say, Joe Biden wins the nomination, then many Republicans and Republican-leaning voters who currently don't have that much of a problem with him will suddenly discover reasons to view him as the devil incarnate. That's what'll happen with whoever wins the nomination. So while Harris might not ever get the kind of polling lead over Trump that Biden has now, Biden himself won't keep that lead if he's nominated either.
The current GE polls just aren't very instructive of how the candidates would fare were they to actually win the nomination, because they have no way of pricing in how voters would actually react to them were they nominated. And that goes for both candidates who are already well know and those who aren't.