Ideas become prominent and then fade. - John W. Kingdon

The phrase "an idea whose time has come" captures a fundamental reality about an irresistible movement that sweeps over the politics and our society, pushing aside everything that might stand in its path.

Flowing along independently of the problems and policy streams is the political stream, composed of such things as public mood, pressure group campaigns, election results, partisan or ideological distributions in Congress, and changes of administration.

People are sometimes reluctant to take big steps. Apprehensive about being unable to calculate the political fallout, politicians shy away from grand departures.