Far be it from me to give advice to political professionals, but I think the Democrats have one option that I haven't heard anyone mention and which I think would be their best play given the mess they're in.
President Biden's poll numbers look very bad, Democrats are demoralized and despondent, they can't persuade Biden to drop out of the race, and they can't force him out without destroying the party. So what can they do?
I think their best move is to persuade Mr. Biden to replace Kamala Harris as his running mate. This would cause a firestorm of protest in much of the Democrat party who would be outraged that an "African-American" female is being shunted aside, even though she's failed to demonstrate that she has the wherewithal to assume the presidency should, as seems exceedingly likely, Mr. Biden be unable to complete a second term.
The solution to this vexatious problem is to pick a replacement for her who would appease the identity politics crowd and energize Democratic voters to come out in November. The pick would be someone who would be eager for the job, knowing that he or she would likely be president within a year or so.
Harris' replacement couldn't be a white male, not in the Democrat party, but it could be someone like Hillary Clinton.
If Biden were to drop Harris and pick Clinton as his running mate Democrats would understand that they were voting for Hillary for president. This might appease the donors, energize the feminists, encourage down-ballot candidates, and perhaps mollify those who chafe at seeing an African-American dissed.
A better choice would be Michelle Obama but she doesn't want it. Hillary doubtless does.
Of course, this move might not be enough to defeat Trump, but it would be better than the status quo and seems to be the Democrats' least bad option.
I hope they don't do it.