Biden was being urged to REPLACE Harris as VP as early as two years ago - as I understand it - in the primary you do NOT vote for a ticket - no one else running has a named VP. VP is named at the nomination. As it stands, had Joe NOT dropped out, he could just as easily named ANYONE else.
We've had years where a previous VP ran against their President, in the primary. You don't vote for a ticket, you vote for a person. I have never heard of a person designating a VP in a primary who isn't an incumbent.
Gerry Ford had Rockefeller as HIS VP - but come the convention - he picked Bob Dole. Just because someone was VP - doesn't put them on the ticket.
All this is pointless as Democrats just make sht up as they go along.