If Team Biden can't allay the fears he is too old, voters will be implicitly pricing in Harris taking his office during the next term anyway. So you either comprehensively demonstrate the "Biden old" stuff is bogus, or if you can't (because true) or can't (because incompetent), get out of the way.
Or to put it another way: every day that Team Biden isn't actually ending the "Biden old" conversation, they are running Harris as the principal at the top-of-the-ticket anyway, but only taking the costs and not taking advantage of the opportunities that come with that
Harris is the Vice President of THIS term, not necessarily the de facto replacement for the NEXT term.
IMHO, if Dems are going to be audacious, they shouldn't temper that because of pretend rules or hurt feelings.
Reliable Dems settled with Hillary in 2016 and then Joe in 2020. In both runups, fervent support for other candidates gave way.
A do over isn't practical. But the platform's the same, the ground game, appointees, and operatives. Not to put it lightly, but the biggest change would be the lawn signs.
