How to you prevent the one time pad from getting intercepted in the mail? If one was intercepted, the person could report it, but then what prevents a nefarious third-party from reporting yours as stolen close enough to the election that you won't get a replacement in time?

Maybe you could pick up your one time pad in person at any US Post Office in the days or weeks preceding the election. You'd have to show valid government issued ID to pick up your sealed one time pad.