Obama is the only one in positive territory among both the general public and among independents. She’s wildly popular among blacks and liked by suburban women. At the same time, she isn’t as disliked by Republicans as progressive senators Elizabeth Warren and Bernie Sanders are. She threads the electoral needle better than anyone else.
Kamala Harris has Silicon Valley’s backing, has the putative requisite experience, and checks the right demographic boxes, but she doesn’t wear well on people. She has the lowest approval rating in the perceived candidate pool (and a net rating lower than Donald Trump’s), including big negatives among independents.