I'm guessing there is already an answer to this, but:
You have a much better chance of getting under or close to invoice if ordering from the factory rather than choosing from the inventory. However, what if the car is in inventory at another dealer and you are requesting a dealer trade? Instead of waiting for the trade, I could simply drive to the other dealer and buy it from them. So would my closer dealer be more open to negotiating if he knew that car I wanted was already ready to buy at another dealer?