The rise of the conservative elite, a self-consciously ideological movement, is a remarkable event in American political history. While today's movement conservatives defend their beliefs as eternal verities, their roots stretch back only to the 1940s, when their intellectual forebears were an obscure fringe and Ronald Reagan was a liberal Democrat.

This brand of conservatism is not a native version of Toryism, classical conservatism that seeks to slow change in the interest of the status quo. Movement conservatives want to overthrow the old regime, the status quo of the past 50 years.

Their use of the "conservative" label is not an ancient tradition. Sen. Robert Taft, the right-wing Republican standardbearer through the 1950s, described himself as a "classical liberal." Only later was the "conservative" rubric draped over the burgeoning movement and "liberal" turned into a term of denigration.

The "classical liberals" of today's conservative movement are believers in the world according to Adam Smith, where harmony is the natural outcome of an economy unfettered by the constraints of government. State intervention to balance the unbalanced after the Great Depression would lead directly to "the road to serfdom," wrote Frederich von Hayek, the progenitor of the modern free market school.

Among free market disciples, the competition of ideas often turns ruthless. The monetarists, led by Milton Friedman, believing that proper regulation of the money supply can restore the lost free market, are under continuous assault from the supply-siders, who argue that tax cuts will restore the market. On many points these theories are fundamentally at odds, though President Reagan has embraced both.

The traditionalists among the conservatives trace their lineage to "The Conservative Mind," a 1953 book by Russell Kirk, who yearned for a hierarchical society bound together by a general reverence for the past. In today's politics, the traditionalist position is expressed in the advocacy of certain social issues -- antiabortion, pro-school prayer, anti-Equal Rights Amendment. Behind these positions is the implicit assumption that a stable conventional culture has been upset by liberal cosmopolitans.

Another strand of movement conservative ideology is anticommunism. The movement's formulations of this old national reflex derive largely from Whittaker Chambers, the Bolshevik transformed into a conservative, from true believer into true believer.

As the witness in the House Un-American Activities Committee investigation of Alger Hiss, Chambers linked an archetypal New Dealer to treachery. Chambers saw the world locked in a manichean struggle of good versus evil, the West versus the East. Liberalism, he argued, was a satanic doctrine undermining our civilization, on the same continuum as communism. Reagan, who has voiced the same argument, awarded Chambers a posthumous Medal of Freedom.

Chambers' views became conventional wisdom among conservatives, and from them flowed the belief in Fortress America -- a strong national-security state that, in principle, contradicts the ideal of a minimal state sought by the free market theorists.

Conservatives have been united less by a shared belief in a prescriptive philosophy than in a shared hatred of their liberal foes. Movement advocates have been most comfortable in the role of defining what they are against.

The greatest organizing principle for conservatives for more than a generation has been Reagan. But when movement conservatism is disconnected from his pleasing image, its internal contradictions may flare into factional warfare. Today the movement accommodates both tolerant libertarianism and strict fundamentalism, free-market Friedmanites and devout Falwellites, an acquisitive younger generation and an austere older one. Without the benefit of Reagan's mediating persona, these accommodations could collapse. Already, a conservative fragmentation is evident. Rep. Jack Kemp (R-N.Y.), the quarterback of the supply-side economics group and putative ideological heir to Reagan, is under attack by many New Right leaders who question the intensity of his commitment to their agenda of social issues -- abortion and school prayer. Vice President Bush, meanwhile, is assiduously courting the conservative leadership, acknowledging its importance in Republican primary politics, where activists often hold sway. The dissatisfaction of some conservatives with these candidates has given rise to much talk within the movement of a possible presidential run by television evangelist Pat Robertson, to whom conservatism is not mere ideology but a matter of faith.

Reagan's continuing presence on the scene has the curious effect of preventing the emergence of another commanding figure. But without one, it may be difficult to sustain the influence the conservative movement has accumulated under Reagan.