[Ed. – There’s something going on, with the complete polarization of the Washington establishment and media against Biden over the Afghanistan debacle. But merely planning to install Harris (a) makes no sense (it wouldn’t change anything policy-wise), and (b) comes with the conundrum of how to get a new Veep approved in a 50-50 Senate. Aside from the question of getting any legislation passed if there’s no VP, there’s the question of the U.S. functioning without a VP. It doesn’t seem to be envisioned by the Constitution and is arguably counter to all constitutional thinking.]
[T]he Democrats have put themselves into such a terrible position that they absolutely cannot get rid of Biden through this means, or else they give up the only chance they have to get anything through the Senate, and they would definitely hurt their electoral chances in 2022 and 2024.
Kamala Harris becoming the President via the 25th Amendment means the Democrats lose their tie-breaking vote in the Senate, and without a 51st vote, there is no way for the Democrats to break a tie in the Senate in order to confirm a replacement Vice President. They are effectively stuck.