I still don’t understand how meaningful in-person voter impersonation would work.

I’m working as a poll worker for the current US election, and I can’t see how you would do it. We don’t check ID.

Right? The person who you impersonated would then be marked as having voted twice, which would pretty quickly get noticed and investigated. So somehow you'd have to get away with that, plus do this at scale so as to actually influence the outcome. Doesn't make sense.