Open Questions to the Democratic Leadership....

Very politely - what is going on that you don't want us to know?
I'm asking this because....
I've heard what Donors and fundraisers are saying. There's a hostile Media (and punditry) and Biden is old has a speech impediment that causes gaffs. He's always had that speech impediment, the Media and punditry has been hostile since Rupert Murdoch moved in. However, Donors and Media aren't the voters, and they can be allayed by the fact that voters and more importantly, delegates are not abandoning Biden.
The strategy in this case would be to do the same thing you did with Obama (you know - that community organizer with little experience who would put off the White Working Class racist wing of the Democratic party?) - coalesce a unity envelope around him, and push back at the Media.

Standard politics. I've some background in history, I've seen how it works. So why aren't you doing it?

Do you want a landslide? Ain't going to happen. You have a Hostile Media that is run for infotainment, outrage and clicks, and you know that. They made bank during the last Trump Administration, and Biden is boring.
Don't know why you think there would ever be a landslide.

Are you afraid of the Supreme Court handing it over to Trump because Biden...what? If the Supreme Court was going to do that for Trump, it wouldn't matter who you ran. Stick with the guy what brought you.

Is there something wrong with Biden you don't want to talk about and you don't think he'll make it to December without embarrassment or ending up hospitalized? Well, you're already embarrassing him, which would make him fight harder. Basic psychology. You're also embarrassing yourselves to the voters because they can't see any change in Biden other than he's older. They frankly see y'all as stabbing him in the back, not a good look if you are running a campaign for yourself. Makes them wonder if you're going to stab them in the back for donors or the Media as well.
If there's nothing wrong with him, put that unity envelope around him and carry on. If there's something wrong with him, make your backup plans while you put that unity envelope around him.

But for the sake of the good Lord above, be honest with both us and yourselves, and don't play could-a, would-a, should-a games this late in the game.

Count your states and the ballot requirements for the General in November at the least. I know if you change the ballot now, you've just lost Nevada in the Electoral college. There's probably other states you'll lose; even if they're polling 65% GOP per the polls now, they're still somewhat in play in November.
I don't know if he steps down for health reasons and Harris goes to top of ticket that might change the rules somewhat, but you can't hound him out.

And please, treat the voters with as much respect as you treat the donors. So far, it doesn't seem like you're actually listening, you're making decisions behind closed doors. And that will depress voter turnout far worse than being honest and working out whatever your apparently sudden problem with Biden is.
He hasn't lost any delegates, and he's doing better as he's fighting. Please don't treat us like we're Q-Anon or MAGA, willing to blindly follow without question.

Yours,
Dawn.S.D, USN (CPO, Retired) AKA Haele on DU

P.S. (Because I'm old school) If you're going to replace Biden, who will you put in Harris' place? If you're going to replace him, you're guaranteed a loss if it's not with Harris. Just my observation as a long time Democratic voter.