High intelligence can either make a politician a better advocate for the interests of the voters, or a better manipulator of the voters. So, just having high intelligence is not enough: one must also consider personality, esp. conscientiousness (moral fiber). Conscientiousness is one of the main 5 personality traits agreed upon my most brain scientists, and the more conscientious a person, the more he will be thinking about "right" and "wrong" when behaving, while someone with low conscientiousness will only be thinking about what's in his own best interest with no concern about the "rights" of others. Most criminals test very low on conscientiousness, and politicians often score low on this trait as well. So, a good politician should have a high IQ and conscientiousness. But, I would not stop there: I would also add that a politician should be very well educated in the field of human psychology as well as a good level of knowledge in general sciences. Also, a politician should have another one of the 5 main personality traits called "open-to-experience." The more open a person is, the more willing he will be to re-evaluate policies to see if better policies are available, or if previous beliefs were based on fallacies. Finally, a politician should be very rational so that empiricism and the scientific method can be used in order to see if a policy will be good or not. Mainstream politicians often ignore science and choose policies based on dogma or "feelings," as opposed to empirical backing.
Regarding society, I think the members of Physics Forums, who make up the cognitive elite of the world, should form their own separate country and thus be free of the low intelligent voters who only bring society down.