In medicine, it has been shown that physicians in the same field tend to have a high correlation with the same personality types on the Myers-Briggs test. I dont know if they are that way going into the field or if the field makes them that way. But I can assure you that surgeons have a very different personality compared to pediatricians. The other thing that has been seen is that physicians tend to be in the personality types that are least represented in the general population and in the types that are the least likely to get along. There is also good data that shows which personality types are most likely to sue.
I dont know about politicians. For the Myerss-Briggs to be accurate, it must be filled out by the individual and honestly. Somehow, I get the feeling that politicians would try to fill out the test based on what they want you to think they are rather than what they really are. I cant help but think that the personality type that goes into politics more often than not is not the same one that tends to make the best leaders. Unfortunately, the types that make the best leaders are not the ones that tend to be the most popular.