The Democrats message is that if you don't vote for them, then democracy dies, literally.
As Democratic Rep. Eric Swalwell says,
I’m worried that if Republicans win in the midterm elections, that voting as we know it in this country will be gone,
In light of the probable chance of losing the midterms and the waning poll numbers of President Biden, the Democrats have attempted to rebrand themselves as the protector of democracy.
Nonstop dramatics about the GOP threat to democracy is part of an attempt to cement Democratic Party hegemony, not ensure election integrity