Ultimately the biggest tell is that women voters are dramatically leading the early vote, they are the slight majority and are even distributed in every state, the reason 2022 was a Democrat tie when historically it is a monumental bloodbath for the party in power (and polls were saying it would be) is the hidden female vote after Dobbs.
The second biggest tell is that internal polling is the only one worth a damn and the Harris camp are confident while Trump has practically given up is avoiding interviews, and is doing rallies in NYC. In 2016 and 2020 he was softening up his image (remember he actually semi apologized about grabbing them by the pussy, the shitstain never says sorry). Instead he is conjuring images of Nuremberg rallies.
Hillary lost in 2016 because there was a monumental demographic shift, and everybody loves an outsider, but Donny is an outsider no more he has a 4 year track record of disaster and we know it will be worse. I don't see the monumental shift again that surprised everyone back then.