Here's the money quote:

She’s running because she’s not Joe Biden. That’s it. The entire theory of her campaign comes down to this: Biden was unfit to run so someone else had to, and there was no practical way to pass over the vice president, so she gets to be the nominee.

There's more in the article.  It's a good read.  Cuts through all the bull.

No one really believes she'd actually, you know... make a good president.  She may be running because she's not Joe Biden (even though she kinda is), but the only reason any voter could possibly have for voting for her is that she's not Donald Trump.  Okay.  If that's your reason, at least be honest about it, and stop pretending she's not really seriously damaged goods.  The Democrats got themselves into a pickle that they couldn't get out of, and she's the result.

Anyway, here's the link:  https://thefederalist.com/2024/10/09/harris-is-only-running-for-president-because-it-became-impossible-to-hide-bidens-decline/