I am old enough to remember a time in which presidential candidates chose running mates on the basis of geographical balance. On occasion, the VP was picked to deliver a particular key state with which he had a strong connection. Ideological balance occasionally entered into the decision, as well. Identity played no role in the process because all of the candidates were white men.
That has changed. Today, the Democrats are primarily concerned with maintaining some sort of identity balance. You no longer see blue team tickets featuring two white men, and you will probably never see one with two women. That is why Harris will pick a white man with ties to the moderate wing of the party as her VP.
it will be Biden-Harris in reverse.