It’s not the sort of thing that is likely to affect the outcome of the race, but I think Biden has botched the veep-selection process. The crucial mistake was announcing early that he was going to pick a woman. It was a mistake to say it even if was planning to do it.
It narrowed his options — and may have narrowed them more than he had intended. Once it was a fait accompli that his running mate would be a woman, attention naturally turned to whether she would be white or nonwhite. At this point, selecting a white woman would be a letdown rather than a (third) chance at a historic first.
It reduced the value of the selection in another way. If he selected, say, Senator Kamala Harris after giving consideration to a large field without demographic restrictions, he could have said that she was the best of all of them. If he selects her now, she’ll be the best he could do among a small list of nonwhite women.