These figures represent an era in which the presidency achieved unprecedented dominance and when the general political consensus reflected a broadly liberal, activist view of presidential power. The New Deal and Great Society programmes of the 1940's and 1960's embodied the belief that the presidency should initiate ambitious social programmes and offer direction and coherence to American politics. Those days are gone, at least for now. Congress is no longer quiescent, the media is no longer reverential. The major parties are now gradually clawing back some of their lost strength, but they are not the great vote-harvesting machines of yesteryear.
Elections are longer, more costly and more reliant upon image and entertainment than ever.
More importantly, they can raise to office Presidents who have only limited regional governing experience and weak ties to weakened party leaders. New technology permits pressure groups to raise the political temperature at will. These groups play a 'zero-sum game'. They are more or less disinterested in compromise or in delay. If congressional horizons are regional, pressure group horizons are narrower still.