If there are enough people hanging around, looking (with keen eyes) over the shoulders of the election workers ... to the point of making them nervous ... If polling places are carefully checked for internet connections during the vote, if voters receive a receipt detailing their vote, if "drop boxes" -- ALL of them, if there are any -- are attended by watchful citizens, a steal would be much more difficult, and much easier to prove if questions arise.
Protecting the vote should be Job One. Everywhere. And if it isn't somewhere, you know exactly who's cheating.
A receipt detailing vote? Like, for whom the vote was cast?
A receipt would mean someone recorded how you voted. That is not needed. Just have an electronic system that prints off the results and you scan that into another machine. Or even the old levers/counters system would be better.