The difference between her and Hilary is that Harris is an avatar of the party, Hilary was (and still is to a lesser extent) a major player in the party

Harris is just like Biden… Her position is the party line. So if Harris is endorsing Mumdani, that signals some faction of the party might be finally waking up and realizing progressives are going to sweep the next election

As for the endorsement itself…I don’t think it dings Mumdani in any way. If anything, I think it just makes him look stronger, because he hasn’t budged an inch and the Democratic establishment is slowly coming to him