retired General Tommy Franks, in an interview with, of all places, Cigar Afficianado, suggests that the U.S. Constitution could not survive the use by a terrorist of a Weapon of Mass Destruction in mainland America, and that the resulting public outcry for security would force, in his words, "a military style of government" to replace it.
Scariest quote from General Franks:
"It's not in the history of civilization for peace ever to reign. Never has in the history of man. ... I doubt that we’ll ever have a time when the world will actually be at peace."