Actually incorrect. It really depends on your congressman's office. I am with Ed Royce in CA. The congressional staffer that runs the application process for nominations is very involved, Patty Shea. She goes out and talks to the USAFA admissions workers (i.e. director of admissions, admissions...
Actually I am a falcon scholar. So at the moment, I am unsure of which nomination got my appointment. My district does not do principal nom. I think I could have possibly gotten a vice presidential nom. This comes from the fact that we only had one slot open and it was taken by a free agent...