I gotta hand it to her. She started off like a boring milk toast politician with that first answer, then she gave a debate performance that debate teams will study for years.
This debate will be THE textbook example of how to counter a machine gun barrage of lies and how to get your opponent talking about your issues.
This made me curious so I looked a bit into it. Seems that milquetoast as an insult originates from an old comic character of the same name, and it's at least feasible (and perhaps likely) that said character was named after milk toast.
I think there was just about the right mix of muting the mics and giving him enough rope to hang himself. Harris' campaign supposedly did want the mics unmuted for exactly that reason, but having them muted did let her get her message across to the viewers without constantly being interrupted.