Just because we made a deal with Iran doesn't mean they are our ally, and I'd hardly call them our "natural" ally; their regime is only marginally less bad on human rights than Saudi Arabia. Iran still funds terror groups, much like Saudi Arabia. They are just part of two different tribes and despise one another. Really the U.S. mission should be to do whatever it takes to prevent Saudi Arabia and Iran from going to war. They are already in a proxy war in several locations, Iraq and Syria being the two largest.

I think that's what people in Washington know, has nothing to do with being their ally and everything to do with stopping an implosion. If Iran got a nuke, it's not likely they would give it to a terror group (from what I see) it's just incredibly likely that it will push Saudi Arabia to get one too and then we'll have quite the situation on our hands.