There are enough other nuclear countries that may deem it nessesary to punish the US for the indescriminate use of nuclear weapons. Particularly those that are down wind.

If things get too hot, cooler heads may prevail deep within the CIA and an assination similar to JFK will occur in an attempt to honor a deal/threat from foreign nuclear powers that be. It is doubtful however since the prez is the son of the former director of the CIA. Still as a sacrifice, it would be easier for George Herbert Walker Bush to bear than losing , say... thier one intelligent son Jeb.

Now lets imagine the head comes of the chicken and daddy Bush dies from a stroke, W goes ballistic, and the Cheney shadow government assumes command to over ride the duly court selected president...

I'm just saying their are more scenarios than we can imagine in a nuclear stakes game.