I can see why there's push back among black voters. K.H. is the safest black lady Biden would dare bring forward as VP; she's very light skinned and not African-American. Black voters very much see distinctions between the tone of skin color. And it can be contentious within the community. I've seen this played out in my workplace.
Specifically, though the term "High Yellow" is considered offensive today, the concept is alive and thriving within the rural black community, and creates more anomisity than people realize. As a child, I remember black folks routinely discussing their less than desireable brethren in less than glowing terms.
I think that is the Camel-uh factor playing in, outside urban areas.