Alas, I'll have to learn to indicate the right level of cynicism more explicitly on here.

As cynical but slightly more in earnest: if voting rights were only given to those who can prove basic reasoning abilities, it might actually make a difference. Since there is no reliable way to prevent authorities from abusing such a criterium, I see no other option than to have no restrictions on any generic criterium. Perhapa a voting obligation would be more effective.