I agree with the posters above. You are probably best off taking some time before applying. When you do apply, you will have to articulate your research interests in a particular topic (or set of topics) within one of these fields (or sometimes at the intersection of a couple). What you've listed here is most of Political Science. As PrinicipalAgent suggested, you should read Political Science journals. Read as many articles as you can make time for and after getting an idea of what these fields look like, pick the topics/approaches/authors that most interested you and delve into them in greater detail. Read other articles by the same author. Read the articles they cited. It's a slow process, but a necessary process for figuring out where you want to make contributions to the field (not to mention, it's not a bad idea to make sure you aren't bored by endless reading of this type before deciding to go to grad school).
Also, you mention that two of your Political Science professors are "supposedly well-known" in Political Science. Look up their CVs and read their articles too. Familiarity with their work/areas of study can't hurt your chances of landing an RA gig with one of them.
When you're reading the articles, it may be tempting to skip/skim over the methodology sections to focus on the theory, results, and conclusions. I would recommend really taking your time with the methods sections and trying to understand exactly what the author is doing to test their hypotheses and why. At first, some of it will probably make you feel like you are listening to the Charlie Brown teacher, but some of it will stick, and it will start to make more sense after a while.