When was that? I always thought the American primaries process was in your Constitution.
Many states have long held party primaries or conventions to select delegates to the parties national convention, but just as the two parties are not in the constitution neither is the method of nominating candidates for the presidency. The process for selecting delegates is up to the individual state and varies greatly from state to state and even then it is up to each political party whether or not they want to participate.
"All you've got to do is own up to your ignorance honestly, and you'll find people who are eager to fill your head with information" --Walt Disney
