It will take a profound cultural shift, to the point where most people use their critical thinking skills to check the veracity of outrageous deep fake media clips. Is that likely to happen? Not really. But even if we can just increase critical thinking abilities by 10% that would be progress.
As a side note, it seems like most politicians who are caught saying outrageous things will do one of two things: deny them vociferously, or proudly brag and confirm that yes, they said/did that. So maybe it won’t be as hard to find the truth as we first think? Though that’s probably just me being overly optimistic.