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The first is rooted in the deep loyalty African American voters have to the Democratic Party and the crucial role they played in rescuing Biden's flailing candidacy and putting him on course to win the nomination earlier this year.

It's an argument that Rep. James Clyburn of South Carolina aired after Biden's black-voter-fueled triumph in that state's primary: "I really believe that we've reached a point in this country where African American women need to be rewarded for the loyalty that they've given to this party."

Abrams has said that "we need a ticket that reflects the diversity of America," and she'd be concerned if Biden doesn't select a woman of color "because women of color — particularly black women — are the strongest part of the Democratic Party, the most loyal."

It also seems notable that Biden faced competition for the Democratic nomination from two black candidates, Harris and Sen. Cory Booker of New Jersey, and neither of them built traction with black voters.

And it raises a question:

If Biden could attract such deep, enduring loyalty from black voters even while facing black opponents, would a black running mate really make him much stronger in November?