Catch phrases? How about "no thanks, but let me know if things change." and walk away. With any negotiation you have to be willing to walk away from the deal. But more importantly, "they" have to know you are willing to walk away, and once you do you must wait for the other party to call back. First one to blink usually looses. This may mean going to a couple of dealerships but it all comes down to how much another 500 to 1000 means to you.