i'm going to say this once and without an in-depth analysis.
right now, voters demonstrate no preference between biden and harris and the debate has had no demonstrable empirical effect on the democrats' polling numbers, which is rather being driven by the weak economy, as measured in terms that matter to working people, rather than terms that matter to stock brokers. this indicates that people that want to vote democrat are voting for the party and not for a candidate. it basically doesn't matter who the face on the party is.
there is currently no empirical evidence to support the idea that harris will perform better than biden, except with black voters, but it is marginal. there is some evidence that harris will perform worse than biden with white voters, but it is marginal.
further, trump is doing extremely well with young male voters, which is a key democratic voting constituency. the swings you are seeing towards trump in key states are happening in the micro-demographic of men between the ages of 18-35, which is a demographic that any democrat needs to win if they hope to secure any election.
by keying in on young male voters, trump is basically pulling the rug out from under the democrats' feet.
harris needs to focus on winning back young men, or she's going to lose states that nobody currently expects are even in play.
the only politician that the democrats have that can counter trump in this key demographic is bernie sanders. harris, conversely, whatever you think of her as an individual, is just about the worst candidate possible to pair against trump.
are the democrats....stupid? it would appear so, kent.