Ability is what interests me most. Faking this sort of content - a continuous, closeup shot of the President saying something - has basically never been possible before. If a total stranger had showed you this video in 1969, it would have been clearly authentic. Not clearly truthful, you wouldn't trust that the landing had really failed as opposed to e.g. Nixon recording speeches for both outcomes. But you could be pretty sure it wasn't an imposter or an edit or anything except the real Nixon on camera.
Deepfakes challenge that ability, but I don't think they'll destroy it. Official sources will sign video. Untrusted sources will use verified timestamping and other methods to prove specific claims about their footage.
Actual knowledge, on the other hand, can't be destroyed by deepfakes because we already don't have it. There are a hundred ways to lie to people - with photoshopped images, deceptive editing, or just lying and having people trust that the evidence exists somewhere. People who aren't easily fooled today will become skeptical about video footage too. People who are easily fooled are already fooled, have been fooled since before photography straight through to the present, and will just stay that way.
"Banning political deepfakes" or anything similar is not just a case of closing the barn door after the horses have left, but without ever getting the horses into the barn.
We do. Even today, very little of what you see in media is entirely real. The alterations are hardly ever as overt as Trotskyites being airbrushed out of Party publicity photos, but that doesn't mean they aren't being done.
Maybe an African-American person ends up looking a little blacker than they really are if they're being accused of a crime, or a little whiter if they're running for office. Maybe they just sound a little more or less "ethnic" depending on whether the press wants them in office or in jail. Or a video is sped up and slowed down at just the right moments to turn a journalist's uncomfortable question into an unprofessional partisan attack.
IMHO we can expect more of these cognitive shenanigans as the technology improves. Manipulation will be performed not just on the subjects in question, but on the contexts in which they appear.
The business model works on "most" people, but not all of them. You can't fight a Fox News with an Air America. It's been tried, more than once. When deepfake material comes to light at the expense of a Democratic president, rest assured, most people aren't going to bother demanding the White House's public key.
All they'll know is what they heard from the talking heads on their news channel of choice: "Well, I don't know, Sean, but a lot of people are saying it's real."