This above passage describes random sampling. Because the researchers pick six random states, then ten random zip codes (for a total of 60 zip codes), then 50 people from each zip code (for a total of 50*60 people), the process is completely random.
Although, I would probably make an alteration to include 3 states that favor one party, 3 states that favor another party, and 3 swing states for a survey like this (with everything still being random).
