There was perhaps a time when a "triumph of politics" would have been something to celebrate, not deplore. But as the title of David Stockman's tell-it-all memoir, it's synonymous with disaster: "Why the Reagan Revolution Failed."

By Stockman's account, so far as the Newsweek excerpts tell it, the "failure" was his own and that of other "radical ideologues" who hoped to use Ronald Reagan's victory in 1980 to streamline the American welfare state. They ultimately got their clocks cleaned by "the politicians," the guardians of "the social pork barrel."

And while Stockman now raises "two cheers for the politicians," the ex-divinity-school moralist in him clearly remains as contemptuous of politics as ever.

For instance, it is his unblushing confession that the "Reagan revolution" was not Reagan's at all. The president, Stockman accurately observes, is a "consensus politician" of temperate instincts whose quarrel was with high taxes, not the welfare state. The radical and revolutionary project of stripping down social welfare to "a spare and stingy creature" was Stockman's and that of the supply-side cabal. That this radical program had never been submitted to the electorate, by Reagan or anyone else, seems not to have bothered Stockman at all.

Stockman's doubts concerning the more self-indulgent aspects of the welfare state were hardly misplaced; nor should these "social pork barrel" programs be exempt from timely review and reform. No, the trouble was that like all elitist approaches to democratic governance, Stockman's was crippled by his impatience with the slow and measured processes of government by consent.

"Our Madisonian government of checks and balances," Stockman now perceptively writes, ". . . is conservative, not radical. It hugs powerfully to the history behind it . . . (and) shuffles into the future one step at a time."

Precisely so. And a good thing too, imasmuch as David Stockman is far from the only solo ideologue who has plotted to dismantle the time-tested labors of other people. One bonus of Stockman's candor, however, is that in telling us how his revolution failed he confirms, point by point, the worst the critics have said of Reaganomics.

They said from the first that the arithmetic of this fiscal "revolution" was all wrong. If you cut taxes radically, raised defense spending geometrically, yet kept the social "safety net" intact, you would have soaring and dangerous deficits. Right, says Stockman, who admits he saw the trouble coming after less than a year.

The critics said also that Stockman and other White House economic advisers cooked their forecasting to brighten the grim prospects a bit. Right again. Stockman admits that he and Murray Weidenbaum, Reagan's first chairman of the Council of Economic Advisers, contrived a phony forecast out of Weidenbaum's "visceral computer," his gut feeling. The gut feeling was wrong by hundreds of billions, but the political purpose was served: "The massive deficit inherent in the true . . . equation was substantially covered up."

This tale of a conspiratorial effort to use a good-natured but inattentive president in pursuit of a "revolutionary" ideological agenda is ultimately shoddy. It recalls the tawdry tittle-tattle of that earlier talebearer, John Dean, without the lawlessness.

It may well strengthen the delusion of every sophomoric antipolitics cynic in America that this is what "really" happens in government. In that ironic sense, Stockman's is the vindication of everything harsh you ever heard Ronald Reagan say about Washington.