Its a coming to Jesus moment for party centrists about being so historically wrong they've been about everything, this entire time. And this is them trying to make up for it in rapid time. This is them realizing they don't and didn't know what the fuck they were doing, ever.
Real answer: We should nominate whoever is most likely to win. The most important and only point is that we need to beat Trump, and we need to stop project 2025. Keeping Biden as the nominee has continuously fucked over our ability to fix this idiotic and stupid unforced error, but here we are. We can fix this.
I think the most electable combination is Kamala + 1. I think that + 1 should be either farther to the left or farther to the right, but regardless you need to get a demographic. The two best options are AOC and Andy Beshear. If you go Andy Beshear, you are trying to pull off NC and GA, and PA. If you go AOC, you are doing so to recover the upper midwest. Andy Beshear is the harder path in an extremely polarized environment; Democrats have been notoriously bad at clawing back votes in southern states. If you go the AOC route, you let her take an oppositional stance on Israel/ Gaza and claw back MI/ MN/ WI.