Perry Anderson in New Left Review:

The American political scene since 2000 is conventionally depicted in high colour. For much native—not to speak of foreign—opinion, the country has cartwheeled from brutish reaction under one ruler, presiding over disaster at home and abroad, to the most inspiring hope of progress since the New Deal under another, personifying all that is finest in the nation; to others, a spectre not even American. For still others, the polarization of opinion they represent is cause for despair, or alternatively comfort in the awakening of hitherto marginalized identities to the threshold of a new majority. The tints change by the light in which they are seen.

For a steadier view of US politics, line is more reliable than colour. It is the parameters of the system of which its episodes are features that require consideration. These compose a set of four determinants. The first, and far the most fundamental, of these, is the historical regime of accumulation in question, governing the returns on capital and rate of growth of the economy. The second are structural shifts in the sociology of the electorate distributed between the two political parties. The third are cultural mutations in the value-system at large within the society. Fourth and last—the residual—are the aims of the active minorities in the voter-base of each party. The political upshot at any given point of time can be described, short-hand, as a resultant of this unequal quartet of forces in motion.

What remains unchanging, on the other hand, is the monochrome ideological universe in which the system is plunged: an all-capitalist order, without a hint of social-democratic weakness or independent political organization by labour. The two parties that inhabit it, Republican and Democratic, have exchanged social and regional bases more than once since the Civil War, without either ever questioning the rule of capital. Since the 1930s there has been a general, if not invariable, tendency for those at the bottom of the income pyramid—should they cast a ballot, which large numbers do not—to vote Democrat, and those at the top, Republican. Such preferences reflect the policies by and large pursued by the two parties: Democratic administrations have typically been more redistributive downwards than Republican, in an alignment shadowing, without exactly reproducing, divisions between left and right elsewhere. But these are rarely differences of principle. A salient feature of the consensus on which the system rests is the flexibility of relative positions it allows. Policies associated with one party can migrate to the other, not infrequently assuming forms in the cross-over more radical than they possessed in their original habitat. A glance at the history of the past half-century is a reminder of these eddies within the system.