Actually, one of my biggest fears about the Iran nuclear negotiations is that Iran is holding out on demands they know that they can't get, but which they are demanding now purely for bargaining room.
So when the Iranians "back down" on these maximum objectives and get "just" the basic agreement that paves the way for Iran to get nuclear weapons, the Obama administration will sincerely believe that they won something significant. They might even believe they achieved "smart diplomacy" rather than understanding that Iran did that to us.
And face it, there's a decent chance Kerry will cave even on the maximum Iranian demands. Why shouldn't Iran try for that when there is no penalty for trying?