I think Harris played it better than anyone had so far with handling Trump. I think her fatal mistep was believing there were hordes of rightwing never trumpers who could be swayed. She had so much momentum when she first stepped in and people thought she’d be further left than Biden, she pivoted further right than him and probably got less votes. Being a POC woman certainly didn’t help either.
I don’t agree that she had no platform other than I’m not Trump, but she certainly shifted right as the race went on and lost more and more support as she did it