I graduated with a Bachelor's in Political Science. The program itself is kind of a shell of what it used to be, but there is one professor your son should take: Dirk Deam. He handles american political theory, law, and also does an environmental class and a space-politics class (he was an Aerospace Engineer who worked for NASA before he became a lawyer and eventually got his PH.D. in Poli Sci and began teaching at ISU). He teaches socratically, challenges students, but is fair and very, very interesting. He also takes time to get to know his students.
He should look over his course listings, and if he sees something he likes, take it. I took every class from the man, and none were disappointing--they were far and away better than most of the rest of the classes offered at ISU. Even if he's just filling an elective (which, the Space class is cross listed in Aerospace Engineering and the Environmental class is possibly cross listed with agronomy... I can't remember, it's a fairly new class so it may not be yet), he's worth taking at least one class with (even if he Audits it). Some students hate him/can't handle him, but he was my favorite, by far, and the one who steered me in the direction I headed (Law). It may not be his interest, but in the spirit of getting a strong general education, no one will do better at teaching the american political process and how it's supposed to work than Dirk.