I think there is a low level panic bubbling beneath the surface of the Democratic electorate.
People tell themselves Biden has beaten Trump before, that Democrats have overperformed post-Dobbs, and that Trump's various legal problems will catch up with him before the election.
But people remember how Clinton was supposed to be a surefire winner in 2016, too, and how popular vote victories don't matter compared to the electoral college, where razor thin margins can turn the outcome.