I believe social activism has been associated with the Democratic Party recently, I suppose it is implied when you run under their umbrella.

It’s rather tricky to fight this perception when it doesn’t primarily come from either one’s messaging or one’s actions.

Not tricky at all: any politician can distance themselves from some fringe group of vocal nutjobs.

Even Trump has done so on occasion, like with the project 2025 conspiracy theory.

Indeed, just denying it while having a ton of actual close ties to it worked in that case.

Or, his voters didn’t care in the first place so the blow was never really gonna land (I suspect this is more like it)

It’s clearly the perception. Before Harris entered the race.

It doesn't need to specifically be Harris or Biden's policies to drag them down. There's very obviously a backlash against some progressive ideology going on, and the democratic party is clearly at least partly beholden to adherents of that ideology. That's why Harris can't give obvious and clear answers to (some) simple policy questions.

Yes, but the claim was they ran on that. Fixing the problem (if it is a problem) is a lot easier, and the necessary approach to fix it very different, if you ran on something and it backfired, compared with not running on it and still losing votes over it.

[edit] I also truly wondered if that’d been a significant part of their message, and I missed it—in the age of granular ad-targeting, who knows?