Chicago Style is the standard for many university press publishers and is used by many programs within the humanities. The American Political Science Association (APSA) based the latest edition (2006) of its own Style Manual for Political Science on the 15th edition of the Chicago Manual of Style. Unless you are specifically directed to use the APSA manual, Chicago Style should be fine, especially since the APSA manual does not reflect the latest edition of the Chicago Manual of Style.
1. The Chicago Manual of Style. 16th edition.
LOCATION: Cabell Reference Desk Z253 .U69 2010
The Chicago Manual of Style Online
Searchable and browsable. Includes both the 16th and the 15th editions.
2. A Manual for Writers of Term Papers, Theses, and Dissertations. 8th edition.
LOCATION: Cabell Reference LB2369 .T8 2013
(NOTE: This manual, commonly referred to as Turabian, consists of the elements of Chicago style most suitable for the individual writer, students in particular)