According to Wikipedia, the most pertinent styles are Chicago and APSA, which is a variant of Chicago. But I could not find stronger references about this.
EDIT. The purpose of my question is the following. I am trying to build a quick help-sheet for scholars and students about the "citation" topic. Political science seems to be a discipline not very careful about the citation styles issue (compared to the STM fields), so I can't find clear information about the practice of its community.