Originally Posted by
King of Nowere
I would equip all voting places with some item that can continuously detect magic (sort of like a metal detector), and a ring/amulet/whatever of protection from evil.
The voters would be scanned for magic, then they would be given the ring to ensure that they would be free from mind control.
Those two items should cost a few thousands gp, so they are affordable. There are ways to fool both, but they require high level magic, so it would be highly unlikely to tamper with elections on a large scale.
If your nation has access to powerful divination, use it on a few random places, just to ensure that high level tampering would have a chance of being detected.
Votes are to be counted directly on the location, by a large number of people, and still looking for magic. It's possible to tamper with the mind of a large number of people, but it's impossible to kep it under cover. You either kill all people involved, which will be a major tip that something is amiss, or the moment they put on the ring of protection from evil (or they roll a 20 on their saving throw) they can tell evereryone that they were dominated.
I guess mind rape would be effective, but if you have the resources to mind rape thousands of people across the country in a single day, then I doubt you can be stopped anyway.