You can also browse subject headings for material. When you pull up a source in the catalog that you like, you can use the hyperlinked subject headings at the bottom of the page to find additional material.
Searching for subject headings can sometimes be tricky since the terms are not always what you'd expect. If you are having trouble figuring out the right terms to use, feel free to ask a librarian for help!
Here are some political science subject terms you can use to get started. For a huge range of sub-heading subject terms, look under political science.