I think that makes many assumptions that could very well be wrong.
These are often double haters. They are tired of both of these old farts appearing confused.
Harris is not a complete unknown. And we’ve seen her out there as his surrogate: she’s got fire, energy, and game. She has the same base of not Trump Biden has, with a chance of winning some of those who are not Biden but not for Trump very much either.
She has to demonstrate truthfulness and energetic fight.
The DNC has no power to do anything but schedule primaries and the convention. They’re essentially part of the Biden campaign. They’ve never had any independent power or influence.
FWIW Nate Silver’s case for and against her. Free.
The people who live and breathe politics and consider themselves professional Understanders of the Average Voter think that “unengaged voters” worry about the same things they worry about and make decisions based on the same factors they do.
I see the disconnect. My “push come to shove” last-second Biden voters are not unengaged voters. Rather, they are simply voters of any cohort that simultaneously (a) are never-Trumpers and (b) responded something other than “Biden” to a poll.
Here you are wrong. It’s not necessarily evidence of senility, as it can be quite normal for stutterers. It can also be a sign of senility. So it’s not that it’s not evidence, it’s just that it’s not secure evidence, and not (of its own accord) enough for a rational observer.
The trouble is, there will be many, many voters whose experience with senile elders included this evidence, and they’re much more likely to weigh their own experience more heavily than abstract possibilities that they don’t have experience with.
In other words, the reasons for calling Zelenskyy “Putin” may be typical Biden, may be evidence of senility, and may be from some other cause, but it doesn’t matter: people are going to jump to “senility” as the explanation, and vote accordingly. The question is, will that be a significant chunk of the electorate or not, and I think the number of such gaffes, and the coverage of them, is going to matter more than the etiology.
Then they definitely should vote for Biden as opposed to the guy who thinks Hannibal Lecter is a real person and claimed to see the late OJ Simpson in the audience at a rally.
I think you are expecting that the third party supporters will vote Biden in the end?
Sorry. Doesn’t look like it.
Of COURSE they should vote for Biden. Everybody should choose Biden over Trump. As I’ve said elsewhere, Biden is the better choice by literally every single measure possible. But you know what? There are people who don’t think so, and they vote.
What is better: pretending that the American electorate will behave sensibly, or trying to understand why they do what they do so we can get ahead of it and prevent this train from running off the cliff?
The problem is getting from here:
To here:
That’s not quite it, either, because upthread I further specified “in battleground states”. That IMO confounds countering analysis based on national polling — yes, I do believe battleground-state undecideds (not “unengaged”) will behave differently from safe-state undecideds.
To me, all “undecided” really means is “something non-commital someone told a pollster for sundry reasons”. I think many of them actually could and would decide if the election were immediately upon them — they just don’t care for reasons to lay it out on the spot for a pollster.
I apologize for not conceding here and for perhaps seeming to move the goalposts around. I think my first post upthread about “last minute voters” laid this out clearly enough, but I can’t revisit it and dive deeply into it just right now. I do feel like something is getting lost in the communication here.
I’ll accept that it is possible that swing state “undecideds”, double haters, disengaged, and third party voters may be different than the national ones. In either direction. No particular reason to think so that I know of, and no evidence of it being the case, but could be! 
The only thing we can do is make the case for Biden. It is abundantly clear at this point that he has zero intent of dropping out, there is nobody who can make him drop out, and polls indicate both that the debate has had no significant impact on the race and that no other plausible candidate polls any better. This scenario where Obama 2.0 comes riding into Chicago like Christ into Jerusalem and electrifies the hearts of the nation is a fantasy and continuing to entertain the idea of Someone Else becoming the nominee only serves to hurt Biden and help Trump.
I wonder if Barack Obama could do it.
(my emphasis)
It’s based on anecdotes, admittedly, both from items posted in this subforum and from things people have said in meatspace. I can give two examples from the SDMB (strictly based on P&E posts, no doxxing).
@PhillyGuy is a frequent contributor to P&E. He’s been consistently against Biden running for at least a year. He posted that he voted for Dean Phillips in his home state’s Democratic primary – in the swing state Pennsylvania. He currently advocates for the position that Biden should leave the race. If a pollster approached him a few months ago, he might’ve gone “undecided” or “other” (correct me if wrong, PhillyGuy). Yet – if I understand his position correctly – on November 5th, if it’s Biden vs Trump vs The Rest, he’s pulling the handle for Biden because he knows it matters in Pennsylvania.
@Boudicca90 posts less often in this forum, but she participated for a time in the “Why doesn’t Biden get traction on the economy?” thread. If my notebook is correct (please let me know if otherwise), she is a never-Trumper, but also doesn’t support Biden in part due to inflation of consumer goods. If polled, she might go third-party (maybe West or Stein) or decline to answer. IIRC, she is in a safe state and thus feels no compunction about voting for someone other than Biden in November.
Now, here’s where I move from real-life Boudicca90 to speculative Boudicca90-like voters who live in swing states. I think many voters (not all) in her particular cohort but that also live in swing states will grit their teeth and vote Biden in November.
I speculate that a lot of “I’m not voting Biden” poll responders in swing states will end up breaking this way in November – kind of like the collapse of the wave form in physics.
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Michigan voter PO’d at Biden over Gaza? For sure … but, damn, I’m going to let Trump have Michigan? Eff it - BIDEN
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Wisconsin voter struggling with grocery prices? But I have little girls at home, and what kind of America are they going to grow up in after four more years of Trump and Project 2025? BIDEN
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Arizona voter concerned that Biden’s too old? But Trump will be back with all that fake elector BS. What the hell - BIDEN
100% of the time? Nah. Enough of the time? I believe so.
I submit that your anecdotes have a huge amount of selection bias, and that even among your anecdotes more would answer Biden than Trump to a pollster.
We, and even your meatspace social group, are not a representative sample of American voters.
To your hypotheticals.
Michigan voter po’d over Gaza. Think our BanquetBear. They can’t vote lesser of what they see as two evils. Third party or skip the vote.
Wisconsin voter. If they haven’t decided to vote for Biden based on their little girl by now? Prices rule.
Arizona voter. Fake electors haven’t bothered them yet? Why later? Trump or stays home.
That’s nationally what the data supports and not hearing any argument let alone data to support an argument that battleground states are different.
Actually, the Trump people are scared shitless that someone other than Biden could run. They have done all their prepping for a contest against Biden. They have no idea how to fight against a different opponent, particularly a feisty younger black woman. Running Harris helps the Dems become relevant again and definitely gives them a substantive challenger against Trump. But it’s also a risk. However, sticking with Joe under the current conditions of his performance is also a risk, and quite a predictable one. Making Harris the candidate would be progress. Plus she’s already on the ticket.