I thought I'd add another comment to the mix of comments made about this film, which is that this film also tackles the issue of Iran's treatment of its Arab minority. This minority lives primarily in a western province called khuzestan (borders w/iraq), and along the western coastline, where the island portrayed in the movie happens to lie.
Most of the local inhabitants that the election official meets speak Arabic, some dont even speak Farsi (like the man in Granny Naghoo's compound). Being semitic, they have different physical appearances from the iranians, who are indo-european. And their customs are more similar to the arabs on the arab side of the persian gulf.
In addition to making points about democracy and about gender issues, Secret Ballot is also about the distance of Iran's central government from its Arab minority, seeming to be out of touch with their customs, their concerns, and their issues.
Incidentally, this theme of how Iran deals with its minorities is also addressed in Baran (Majid Majidi), but in that case it's about Iran's Afghan minority.
Congratulations to Babak Payami for a wonderful little gem of a movie.