I fudged on the title a bit, which is actually "Light rail, Heavy Eating: An Exercise in Rationality in Politics." It uses a restaurant example (and some simple number crunching) to get at concepts of "rational ignorance" to show why Americans can be against budget deficits (in general) and merrily vote for their free-spending representative at the same time, and asks students to brainstorm reforms. Can be used as an in class activity and/or the basis of an assignment. Includes a grading rubric.
This assignment ultimately has the students figure out why Americans hate big government, and continue to vote for it--because it's rational.