This had better become required by law, and soon, if the government wants people to trust electronic voting machines. Every security expert who’s even glanced at them has been appalled at how easily they can be manipulated.
Related and possibly-interesting note: a significant part of one of the Stainless Steel Rat books — written long before the first electronic voting machines made their debut — revolved around a rigged electronic voting system. The main character knew that the electronic system would be rigged, and was counting on it, because he’d found a clause in the constitution of the planet in question that allowed him to force a manually-counted election if the electronic one was shown to be grossly in error. The manual one was even more rigged than the electronic one, but since it was manual, the current
dictator President found it much harder to cheat — and the good guys found it much easier. The end result was very, VERY close, but I’m sure you can guess the outcome. 🙂