It likley depends upon which school you are negotiating with and what cards you hold in your hand. I know a person who declined an offer of acceptance at one school last year after having chosen to attend another school. The declined school thanked the person, but told them that the offer still stood if they changed their mind. That situation may not exactly fit your scenario. One word of caution. I would not try to bluff your hand, because I remember reading somewhere on this forum that all the schools receive a list of who has been accepted where.