How are public policies initiated in American politics?  Do they spring fully formed from the furrowed brow of the President?  Are they the product of congressional committees?  This pathbreaking book by Nelson Polsby looks for the first time at the process of political innovation.  Drawing examples from foreign and domestic policy, Polsby examines the genesis of eight major new government initiatives: the Peace Corps, the Truman Doctrine, the Council of Economic Advisers, Medicare, Community Action Programs, the National Science Foundation, civilian, control of atomic energy, and the Nuclear Test Ban Treaty.   Polsby has explored empirically the preconditions of political innovations, and he draws conclusions that have general applicability for the understanding of innovation in the American political system.  His characteristically witty and stimulating book opens a third branch of inquiry in political science--on a coequal footing with the study of legislative enactment politics and the study of policy implementation.