The only thing democrats recognised was they were about to lose, and lying to the American people about Joe's health wasn't cutting it with their donors.
Consider this analogy. A 10 round boxing match is in the 8'th round and one boxer is losing badly. The coach seeing that his guy is losing now brings in a new fresh team to take-on the other guy. Sport events don't allow the replacement of an entire team. This is dishonest.
There is no "rule" prohibting the swapping of Biden for Harris. Nevertheless, the Democrats contend that they are the ones protecting democracy. Swapping Harris to replace Biden was not done through a democrtic process. Democrats broke their own "rules". For Democrats, the ends justify the means. Democrats have no ethics.