The former seems less and less likely with each passing hour of media vulture feasting on all the Biden body parts the NYT keeps tossing around.
And the latter strikes me as pure fantasy based on everything I know about how campaigns work.
The latter is why if there is a replacement it'll absolutely be Harris; she's already a candidate for this specific campaign and could continue to use its funds/infrastructure.
My cope about the latter is we're so far out of the range of normal events the standard assumptions may not apply. Although jfc are people underestimating how complicated this will be
Also the Heritage Foundation drooling at the chance to challenge ballot access for a new candidate fills me with dread, since we all know what happens when that goes to the courts.