I seriously doubt going to the center wins any votes in the general.

I think this is the only point where we have a real disagreement. There were indeed folks who split their ticket in 2020 - voting for Biden-Harris but otherwise voting for all GOP, see https://www.texastribune.org/2020/11/16/split-ticket-voting-texas-republicans/

See also this chart, showing that such a split ticket is about 4% out of everyone who voted: https://www.pewresearch.org/politics/wp-content/uploads/
sites/4/2020/10/PP_2020.10.21_split-icket-voting_0-01.png

Now, it just says that 4% of voters split R/D. But I can't imagine anything more than a negligible amount were from Dems who voted for you-know-who as President. Therefore, that 4% can be attributed to Republicans who voted for Biden.

Maybe this would have happened anyways, but I suspect that going rightward made this kind of split easier for those folks to swallow.

Finally, look at the small margins that Biden won on the swing states according to https://www.npr.org/2020/12/02/940689086/narrow-wins-in-these-key-states-powered-biden-to-the-presidency. So what this could mean, assuming that the 4% holds generally, is that the 4% difference cause by split voting is greater than the margin that Biden won in those swing states. If Biden was too leftie, he might have lost those votes - and those states - and the Electoral College.

in the end it’s an excuse to more deeply entrench the oligarchy and it turns off people who need something to be excited about in order to bother coming out for the general.

I feel like Harris is coming up with new strategies on this point to compenstate, like getting on "Call Me Daddy" and Howard Stern, along with powerful endorsements such as Taylor Swift's.

I can’t imagine young voters were happy to hear Harris at the debate talking about how she’s going to expand oil drilling.

Yeah, it shows what a struggle it is to go with the centralism strategy - staying too far left may cost the votes needed to win the EC but going too far right may cause faithful voters to sit the election out, which may cost the popular vote - and thus the EC if it's bad enough.

Biden won because leftists were energized about getting Trump out of office,

Agreed, this was definitely a reason

not because centrism won over conservatives.

I think both might have been contributing actually.

And there are probably many others. Here's one third factor - 2020's election happened just mere months after the pandemic. The president at the time was in denial and a lot of people died due to the mismanaged response - and that may have been reflected in the votes.

I think the centrism is why he was projected to lose this year! Gaffes and age notwithstanding, even a perfect public speaker wouldn’t have had much to work with.

My impression was that Dem party leadership and donors took action after seeing the debate - and that was primarily because of age and gaffes. Of course, upper management and the wealthy tend to skew someone conservative anyways so perhaps not the best sample.

But I firmly believe every move she makes to the center is doing more to turn off leftist voters than it is wresting people from the right.

I really hope this is not true. I kinda feel she really needs both sets of votes right now to win. It didn't seem to be true in 2020 - but of course 2024 is a different year, and more importantly Harris is a very different candidate from Biden.