True of literally every candidate you put forward. You need to not only demonstrate that some Democrats will stay home because Biden is old, you also need to demonstrate that fewer Democrats will stay home as a result of another candidate's weaknesses
If you put up Harris, some Democrats are going to stay home because they don't like voting for a former prosecutor, or they find her off-putting, or the New York Times runs a bunch of stories about "what did Harris know about Biden's health????"
The thing that makes it a lot easier to deliver a message? When your candidate can reliably be understood when they are delivering a message. I can’t believe we are even debating this.
I can only say what I said before: Biden is worryingly behind in the polls. His own campaign insisted on this debate to change that dynamic. It made it worse. I would be delighted if he were able to turn this around. I don’t see that happening.
If you're going to keep saying that he is worryingly behind in the polls, you have to at some point address my repeated observation that he is not, according to the averages, particularly far behind.
The state polls are similar. Anywhere between +2 and -2. 538's model has the race as a coin flip for a reason.
Would I prefer he were polling better? Yes. But it's July and these are nowhere near insurmountable numbers.