In olden days, the U.S. Communist Party specialized in factional fights, one of which concerned the deviationism of Jay Lovestone, whose enemies' slogan was: "Lovestone is a Lovestoneite!" They had him there.

David Stockman's case against Ronald Reagan is: "Mr. Conservative is a conservative!" The title of Stockman's instructive memoir -- "The Triumph of Politics" -- is a lament and is rich in paradox. It could be "The Triumph of Conservatism" -- the president's conservatism and the American people's.

"The Reagan Revolution," writes Stockman, "as I had defined it, required a frontal assault on the welfare state." Precisely: as Stockman, not Reagan, defined it.

The "revolution" was to have had two parts, the tax cut and whatever spending cuts were necessary to pay for it. Reagan got most of the former and little of the latter, creating an imbalance that was made worse by Reagan's finest achievement -- the conquest of inflation. Cutting inflation was like another tax cut: the postwar growth of government was largely financed by revenue raised by "bracket creep," as inflation floated taxpayers into higher brackets.

The book is basically a history of 1981 up to November, by which time Stockman knew -- ready for this? -- that Congress was more eager to cut taxes than spending. Beginning in 1981, many Americans had their bluff called. They had become comfortable with their rhetoric of complaint about "big government." But the 1980s have been a crash course in the federal budget. There has been a rolling referendum on domestic spending. After a cold shower of facts, the country is wiser but also sadder, because it now must forgo the fun of feeling virtuous merely by generalized antigovernment thunder.

Stockman's "revolution" rested on the theory that the "will of the people was at drastic variance with the actions of the politicans." But Reagan turned out to be "a consensus politician, not an ideologue." And the consensus? The voters did not vote for radical discontinuity, for a revolution against the post-New Deal role of government.

Stockman says "the dirty little secret of the Republican Party" is that 80 percent of House Republicans and 90 percent of Senate Republicans voted for the major expansions of the welfare state during the past 30 years. Secret? Only ideological spectacles let Stockman reach age 34 unaware of the fact that the modern state is not an accident or a conspiracy foisted on the nation -- the Americans really do want mild social democracy, sacrificing some capitalist efficiency in the interest of equity and security.

Stockman convicts Reagan of moderation and prudent skepticism about ideology -- conservative virtues. He acquits Reagan of a serious charge against him. The charge is that Reagan launched a savage attack on the social "safety net." If Democrats wonder why the country is not seething about Reagan's "frontal attack on the welfare state," they should read Stockman. The "attack" was a peripheral skirmish waged with only a smidgen of the ardor Reagan reserved for cutting taxes.

Stockman's book is full of phrases like "It had started to dawn on me . . ." and "I was finally beginning to see that . . . " What so slowly dawned on him were some (to him, unwelcome) truths of conservatism. Our government "is conservative. . . . It keeps powerfully to the history behind it." And: "History in a democracy does not live to be rewritten and rerouted; it just lives for another day, finding its way into the future along the trajectory of its well-worn and palpable past."

Six years ago -- how quickly we forget -- there was abundant worrying about Reagan's age. Stockman's book demonstrates how youth can be a menace to good governance.

The huge deficits clearly show that Reagan was wrong about his capacity to cut the budget and the stimulative effects of the tax cut. But no Reagan miscalculation matches Stockman's spectacularly bizarre belief that the political system had given the country a welfare state the country never wanted or that the country had suddenly stopped wanting it.

Perhaps Reagan just thought: What the hell, let's try cutting taxes and spending and see what happens. Reagan -- why can't intellectuals concede this point? -- may know a thing or two, including this: economics is a science of single instances, so we know less than people like Stockman think.

Stockman chastises himself but remains essentially unchastened. There is an offputting tone of knowingness to this book that now arrives, overflowing with condescension toward Reagan, in the midst of an economic boom. One theme of Stockman's book is that Reagan's intellectual insufficiencies include too little knowledge of economics. The largest lesson of the book is that Stockman knew too little history and politics, and perhaps economics too.