Hi, If you don't ask you won't get ! I'ts always worth asking if it's their 'Best Price' espesially at the moment when everybody is desparate to sell. It will make a difference if the car has been there for a while and how serious you are about the purchase. You do not say whether the car you fancy is new or used and whether you are trading one in. If you are trading in I suggest that you get a price on your old car before you ask for a reduction on the new one.
My wife and I were offered a reduction on a new car at a Supermarket. It was a compeditive price to start with but had been there for some time. As it happens we walked away from this offer as we were given a great deal at a dealership !