look - I'm receptive to both "no, it's gotta be him" arguments and "he's gotta step aside" arguments. not to be wishy-washy but both arguments have merit. "then we do a tourney" is OTOH flatly hilarious. yeah that'll go great. there will much much unity in the wake of the electoral deathmatch
Harris was a great choice a year ago but unless Biden claims a sudden stroke or something she'll be dogged with "When did you learn the president was unable to fulfill his duties and why didn't you act then?" It would sink her chances.
Harris is the ONLY other logical choice but, barring a "sudden" Biden health catastrophe, she has no chance of winning. They'll just paid the Dems as liars who left America vulnerable with a feeble POTUS and that she knew.
Any elected Democrat you've ever heard of has a chance against Trump if the party can consolidate behind them. This is not to say that they are strong but that Trump is weak.