A lot of people polled (like 28% in one case) say they want to know more about Harris. This is not true for Trump. So, as long as Harris represents herself well in the debate, she has the opportunity to win lots of votes.
If she can't avoid getting pantsed by Trump in a singular debate then she probably doesn't deserve to be president. I think this is a good calculated risk because she does need a bit more out there for people to digest and refusing to debate Trump just makes it look like she lacks confidence imo.
I don't disagree with this at all, but she has to be pretty close to perfect, while Trump will be allowed to lie and be mostly incoherent like he always is. I'm still not sure it's worth the risk for her based on what happened after the Biden debate. Trump said all kinds of crazy crap and every website, tv show, etc. just said, "look how old Biden looked". She has her chance to turn the table, but it's still a big risk.