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...what we're doing is making predictions based on only part of your search - specifically, the last word or words. While few people have searched for [florida state senate building], many more have searched for [state senate building]. By looking at just the last part of what you've typed into the box, in this case "state senate bui," we can generate a prediction for "building." You'll see a dropdown box below the end of your search with predictions for just that word.
Sounds pretty clever, and it will probably send Google Suggest scraper tools back for a re-coding, too.