I think the number of votes lost because of race or gender is not 0, but the gains through reinvigoration are far, far higher.
We don’t know, that’s what makes this scary. I’m more pessimistic. IMO the whole reason Trump got elected in the first place was backlash over the first black president. I think the US is a lot more sexist and racist than people want to admit. Even people who don’t think they’re racist or sexist will still show huge cognitive biases in an unconscious bias test. So, they’re not going to say “I’m not voting for Kamala because she’s a non-white woman”, they’ll say “I’m not voting for her because she’s underqualified” or “I don’t like her record as a prosecutor” or “she doesn’t seem like someone I’d want to have a beer with”.