Events in the Oval Office on Monday, March 20, 1973, reveal much of the Nixon presidency in shorthand. The president began the day schmoozing with Republican leaders, a chore he disliked. Party loyalty was necessary but inhibiting. The meeting did give him ideas, however, about deflecting criticism of official secrecy by proving that Lyndon Johnson was worse.

The twilight of Watergate was settling in. But Nixon and his closest aides still underestimated its implications, nine months after the event. This day Richard Nixon fussed over Watergate statements drafted for the public ear, bypassing media critics and Senate investigators. Nixon "feels strongly that we've got to say something to get ourselves away from looking like we're completely on the defensive and on a cover-up basis," Chief of Staff H. R. Haldeman recorded for his journal. The problem was that the president -- and Haldeman -- already were knee-deep in the cover-up that would drive Nixon from office 16 months later and send Haldeman to prison for conspiracy and perjury.

The president also fretted that day about whether to answer North Vietnamese truce violations with bombing. Henry Kissinger, the temperamental national security adviser, was on holiday. Nixon's exasperation with Mr. Kissinger is one of the recurring, frequently amusing, themes of Haldeman's diary. Mr. Kissinger was terrified that Secretary of State William P. Rogers was out to get him, and vice versa. Each was right. Most outsiders called it a mismatch favoring Mr. Kissinger, and it was he who survived.

Nixon and Haldeman coddled Mr. Kissinger until finally Haldeman challenged one of his frequent threats to resign. Mr. Kissinger retreated. His own sense of humor helped: Even paranoids, he said, had real enemies.

But Mr. Kissinger's salvation was his brilliance as historian and political strategist, including his understanding that even failure may succeed. Failure was the predictable fate of negotiated American withdrawal from Vietnam. Yet at least some blame fell directly on North Vietnam for betrayal, and Americans had time to adjust to defeat.

Haldeman's book is history created at the highest level by the lowest means. For 1,521 days, until Nixon offered him up as a Watergate scapegoat, the president's chief of staff recorded the presidency in flat, unadorned prose. A California advertising executive, Haldeman was the person closest to the president but never his friend. He accepted the appellation of "Nixon's SOB" without rancor because the reputation enabled him to make life easier for the boss.

The Richard Nixon who emerges from these pages will surprise no one. But there are precious details that already have sent historians rushing to other records, comparing, analyzing, still trying to understand one of the most complex administrations in American history. Indeed, Nixon's cynicism, his readiness to lie as a means to any goal, his hatred of the news media and his contempt for liberals, all confirmed here, may have been even greater than Nixon-haters assumed.

Anti-war protesters of the period will learn that Nixon welcomed their clamor for its impact on Middle America. Consider Haldeman's report after a Nixon appearance in San Jose, Calif. Demonstrators, Haldeman recounts, "tried to storm the doors after we were in, and then really hit the motorcade on the way out. We wanted some confrontation and there were no hecklers in the hall, so we stalled departure a little so they could zero in outside, and they sure did. Before getting in car, P [the president] stood up and gave the V signs, which made them mad."

George McGovern had Nixon's private support as he sought the Democratic presidential nomination in 1972. Nixon "made the point that the most effective way now for us to build McGovern is to get out some fake polls showing him doing well in trial heats," Haldeman wrote. Nixon favored Mr. McGovern because he would be easy to defeat in November.

Nixon raged steadily at the news media and tried to bar writers of unfavorable stories from the White House. He was frustrated when editors were unimpressed by his complaints and even his staff hesitated to anger journalists.

It would be laughable understatement to say Nixon was politically incorrect. But it would also be wrong to brand him simply as anti-Semitic or racist. True, he railed at support of Israel by American Jews. True, he saw the "whole problem" of welfare as one of blacks. But Nixon saw offending Jews and blacks primarily as obstacles to his designs. The distinction may be no more attractive, but it is a distinction nonetheless.

Nixon critics inclined to sanctimony should be cautious enough to imagine their own heroes in the light Haldeman sheds. It's improbable that a Haldeman would have added significant insights into the character of, say, Jimmy Carter. But that cannot be said of John Kennedy or Lyndon Johnson. After all, the argument is made that Jack Kennedy's men stole the presidency in 1960 -- from Richard Nixon. Haldeman leaves no doubt that Johnson and Nixon held each other hostage to charges of dirty tricks.

Journalists who were Nixon targets also might reflect whether they really, truly remained fair and dispassionate in their coverage of the White House. In some cases the answer is demonstrably no. But does the answer even matter? The abuses were there to be covered, whether or not those covering them enjoyed sticking it to Nixon.

But all else fades beside the importance of this book to the Watergate record. Enough time has passed to justify a reminder for a new generation; Watergate means far more than the building that housed the Democratic National Committee. It embraces the cover-up that followed the bungled burglary of the DNC by super-macho Nixon loyalists.

Haldeman's diary is condensed here by 60 percent from the original, which is available in full for $70 on CD-ROM. But the book contains every word he wrote about Watergate, including, he says in his introduction, all those things he wished were unsaid and undone. Shortly before he died last Nov. 12, Haldeman announced that he was making it all public to complete the record, especially for scholars and journalists.

Haldeman rarely quotes principals directly in Oval Office conversations. Most often he paraphrases. Thus he does not use the president's words on June 20, 1972, when Nixon proposed ordering the CIA to claim national security and divert the FBI from the Watergate investigation. Nixon's exact words, recorded White House tape, became the "smoking gun" when they were discovered that forced his resignation more than two years later.

But Haldeman's reporting makes clear that the Watergate break-in was merely a nuisance, treated in passing, during late 1972 and early 1973. Carelessness, more than design, led the president to slip easily and naturally into the cover-up, including support for payment of hush money to the burglars.

Later, when it was apparent that the presidency was at stake, Haldeman reviewed some of those early tapes to assess the president's culpability and presumably his own. Inexplicably, he concluded that the discussions of hush money -- blackmail payments, less politely -- might be manageable. To any unprejudiced ear they were disastrous.

Thus Haldeman himself becomes proof that even at exalted levels the instincts of common morality are dulled by repeated abuse. The line between pragmatism and excess dims. The thermostat malfunctions. That it occurred so naturally may be the most terrifying aspect of the whole episode.

Mr. Trewhitt, a former diplomatic correspondent for The Sun, teaches journalism at the University of New Mexico.

Title: "The Haldeman Diaries: Inside the Nixon White House"

Author: H. R. Haldeman

Publisher: Putnam

Length, price: 698 pages, $27.50