It’s literally name recognition. Harris and Biden are genuinely unpopular and prominent. I recently rattled off half a dozen names of potential replacements, governors and senators, to a bunch of lib friends and the literally only recognized newsom and they are John Stuart watchers and watched the debate meaning they are not completely disengaged.
On the head to head polling posted yesterday buried deeper in that same poll it showed that most respondents really did not know any of the dem replacements. A lot of Biden being ahead of everyone was plain name recognition. https://x.com/umichvoter/status/1807449998256419136