Professor Theriault, who is fascinated by congressional decision-making, is currently researching the effect of interpersonal relationships within the U.S. Congress. He has published five books: Congress: The First Branch (with Mickey Edwards; Oxford University Press, 2020), The Great Broadening (with Bryan Jones and Michelle Whyman; University of Chicago Press, 2019), The Gingrich Senators (Oxford University Press, 2013), Party Polarization in Congress (Cambridge University Press, 2008), and The Power of the People (Ohio State University Press, 2005). He has also published numerous articles in a variety of journals on subjects ranging from presidential rhetoric to congressional careers and the Louisiana Purchase to the Pendleton Act of 1883.