Reddit reviews The Affect Effect: Dynamics of Emotion in Political Thinking and Behavior

Political psychology, although typically considered a subfield, covers a wide range of variables (e.g., personality, decision-making, behavior, beliefs, emotion, conflict) from multiple levels of analysis (e.g., individual, group, state, system). Given that your thesis will inevitably consume a great deal of your time and effort, you'll want to focus on an area of political psychology that you find particularly interesting. Here are some resources that can help you pinpoint a topic:

• Political Psychology (the most prominent academic journal dedicated to political psychology)
• Political psychology (Wikipedia) [the list of prominent political psychologists toward the bottom of the page provides a decent starting point]
• The Oxford Handbook of Political Psychology (Huddy, Sears, & Levy)
• Introduction to Political Psychology (Cottam, Dietz-Uhler, Elena Mastors, & Preston)
• Political Psychology: Neuroscience, Genetics, and Politics (Marcus)

However, it occurs to me that providing you a few links and telling you to "read!" might not be the most helpful approach, since I'm pointing you toward a forest when you eventually need to locate a specific tree. Does your college/university offer any courses that relate to political psychology? If so, I would consider taking them (or at least reaching out to the professors that offer them). [Note: Even if there aren't classes dedicated to the subject, your university likely has related courses (e.g., American politics, social psychology) that might be useful]. In my opinion, taking courses or talking to professors will likely benefit you even more than independent reading.

And lastly, since you asked, here are some specific areas of research (that I find intriguing), along with relevant recent publications (that I have enjoyed):

• The structure and determinants of political ideologies: 1, 2, 3, 4
• Personality characteristics in the political domain 1, 2, 3, 4, 5, 6
• The dynamics of political information processing: 1, 2, 3, 4, 5, 6, 7, 8
• The efficacy of biological and neuroscientific explanations of political behavior: 1, 2, 3, 4, 5

Maybe one the aforementioned topics will interest you. If not, there are plenty other research foci out there (you might have noticed that I failed to include a topic related to foreign policy, a literature to which I haven't paid much attention recently). Best of luck!