They need to have rehearsed and prepared talking points because that's the only way they'll actually come across as standing for anything other than the status quo, which is deeply unpopular. Most democrats probably don't even know what they even theoretically stand for without a corporate donor explicitly telling them what to do, and most of them can't do improv on the level of even being able to make shit up or lie in the absence of that, much less to charmingly lie by omission or tell the truth by technicality.

I'm not sure what you're talking about. Harris's message was along the lines of (from a Lemmy comment, TBF), "address disparate health care outcomes that predominantly impact Black men." Nobody even knows what that means, much less has the ability to remember it. Or, she had some talking point about a several-thousand-dollar tax credit. (I don't recall how much or for whom.) That is, they talked like policy wonks, not in terms like "dignity" and "providing for your family" that reach people emotionally.

Their opponents said highly memorable-but-evil things like, "Haitian immigrants are eating the pets." I mean, like that, but good. Or, when you think of Obama, there's one word that immediately comes to mind. Like that.

ETA: I just remembered one of Harris's other leitmotifs for the campaign: "We're not going back." Just awful messaging. Democrats constantly, constantly, go for the negative formulation, which is terrible messaging. For one, saying you're not your opponent lets your opponent control the terms of the debate. Also, our memories and subconscious minds are bad with negatives. Like the famous pink elephant example, if I were to say, "I'm not a professional dogcatcher," a week from now, you might have the vague recollection of u/SwingingTheLamp and dogcatchers, or maybe just dogs. If I were smart, I'd say, "u/SwingingTheLamp is such a sexy guy" instead.

This particular example doesn't suffer from that problem, but on the other hand, it doesn't say anything of importance. So we're not going back, great, we already knew that, but where are we going? It doesn't say anything emotionally-impactful about the future and Harris's role in it. By contrast, "make America great again" is much better slogan, because it makes a promise about the future. And a vague one, so you can seamlessly fill in whatever you think "great" looks like, and you can actually envision a perfectly-tailored picture of the future. Harris == discontent about the past; MAGA guy == good-feels about the future.