WATERGATE: THEN AND NOW : Watergate Echo: What Do We Know and How Do We Know It? : History: It was the political investigation of the century, but even answers that seemed clear 20 years ago have grown a little cloudy over time.

“What did the President know and when did he know it?”

That question, repeated endlessly by then-Sen. Howard H. Baker Jr. (R-Tenn.), set the tone for the investigation that ultimately forced President Richard M. Nixon from office, the only presidential resignation in two centuries of U.S. history.

And when Nixon admitted defeat in his two-year fight for political survival, the answer seemed pretty clear: “The President knew just about everything about crimes committed in his name and he knew it very early.” That conclusion, shared by a majority of the Congress and much of the public, was based on millions of pages of evidence, including one taped conversation that even the chief White House lawyer called a “smoking gun.”

But now, 20 years after the botched burglary at the Democratic Party’s national headquarters touched off the nation’s most perplexing political scandal, nothing seems quite certain anymore. Nixon, assiduously working to restore his reputation as a wise elder statesman, has just completed a visit to Russia where he was afforded VIP treatment by President Boris N. Yeltsin. And revisionist writers are suggesting that Nixon himself was the victim of dark conspiracies.

Twenty years after the word “Watergate” became a synonym for corruption and abuse of power, there are still questions without answers. And the public memory of the affair, once so fresh, has faded to such an extent that the answers to some questions simply have been forgotten.

According to a recently published book by Michael Schudson, a professor at UC San Diego, a third of all high school students today cannot name the President who resigned or place the date of the Watergate burglary within 20 years of when it took place: June 17, 1972.

“Different views of Watergate have warred with one another through the past 20 years, underscoring the vulnerability of history,” Schudson said.

But when Nixon announced on Aug. 8, 1974, that he would resign effective at noon the next day, only his staunchest backers expressed much doubt about his involvement in the Watergate cover-up and in a variety of other charges, including misuse of the Internal Revenue Service to punish political enemies, misuse of the FBI and illegal spying on U.S. citizens. The House Judiciary Committee had approved a bill of impeachment and Nixon admitted that his options had been reduced to two: resign or be impeached.

By quitting, Nixon stopped the congressional impeachment investigation in its tracks. And, less than a month later, when President Gerald R. Ford pardoned Nixon in advance for any criminal conduct, it effectively ended all official investigations of the President’s conduct.

The abrupt end of the investigation left a few intriguing questions unanswered. Despite almost 20 years of probing by journalists and others, the most important ones still remain open:

- What were the White House burglars after when they twice broke into Democratic Party headquarters in the Watergate complex?

- Who was “Deep Throat,” the mysterious but obviously well-plugged-in source who provided inside information about the federal investigation to Washington Post correspondent Bob Woodward?

And most intriguing, and confounding, of all:

- Why? Why would operatives of one of the most savvy political organizations of the last half of the 20th Century risk everything to spy on a party headquarters in an election year in which Nixon was already an odds-on favorite to win?

That last question is so imponderable that it implicitly formed the core of Nixon’s defense. From the moment that five operatives of the Committee for the Reelection of the President were arrested in the Watergate complex, the explanation offered by Nixon and his lieutenants was, in effect: “We couldn’t have been involved; we aren’t that stupid.” White House Press Secretary Ron Ziegler called it a “third-rate burglary.”

This remains Nixon’s defense to this day. In his 1990 book, “In the Arena,” Nixon remarks: “Whoever ordered the break-in evidently knew little about politics. If the purpose was to gather political intelligence, the Democratic National Committee was a pathetic target. Strategy and tactics are set by the candidate and his staff, not the party bureaucracy. Moreover, in view of the 30% lead I had in the polls, it made no sense to take such a risk, because the likely Democratic nominee, Sen. George S. McGovern, stood virtually no chance of winning.”

Logical as that may seem, it certainly does not prove that the burglary did not take place--only that its purpose was not to gather political intelligence. So, why?

The most likely hypothesis is that the White House wanted to find out what the Democrats and their chairman, Lawrence F. O’Brien, knew about Nixon. The June 17 incident was the second time that the burglars had broken into O’Brien’s office. It was intended to repair a bug left on O’Brien’s telephone on the first occasion, May 28, 1972.

James W. McCord Jr., security chief for the Nixon campaign who led the burglars and served 69 days in jail for it, recalled long after his conviction that he never knew what he and the others were after. He said it was basically a photographic mission and that G. Gordon Liddy, the man in overall command, had mysteriously told him: “I want want you to photograph any papers on Larry O’Brien’s desk that have a dollar sign on them.”

Sam Dash, general counsel of the Senate Watergate Committee, said in a recent interview that he believes the White House wanted to find out what O’Brien might have known about the relationship between Nixon’s brother, F. Donald Nixon, and reclusive industrialist Howard Hughes.

“We know that Nixon was so concerned about his brother that he asked (Atty. Gen. John N.) Mitchell to find out what might be known,” Dash said. “Larry O’Brien also worked for Hughes as a consultant. Their paranoia would make them believe that Larry O’Brien might have that material.”

Another theory is that O’Brien might have had evidence of an illegal campaign contribution to Nixon from the right-wing dictatorship then governing Greece.

One thing seems certain, however: Whatever the burglars were looking for was never there. If the Democrats had possessed truly damaging information about Nixon, there can be little doubt that they would have used it.

As for Deep Throat, Woodward revealed his existence in “All the President’s Men,” the book that he and Carl Bernstein wrote about the scandal. But Woodward has never named the source and no one has stepped forward to claim the honor.

Much of the speculation has focused on White House insiders like Alexander M. Haig Jr. or Leonard Garment. But this seems far-fetched because everyone in a position to know what Deep Throat apparently knew was a Nixon loyalist who would be unlikely to leak damaging information to the press.

Dash believes that the source was a composite of several individuals because “no one person in the White House would know it all.” But Woodward insists that the source was a real person.

Los Angeles Times reporter Jim Mann, who worked at the Washington Post during Watergate and knew Woodward, theorizes in the May edition of the Atlantic that the source was a high official in the FBI. He reasons that the bureau was furious at Nixon’s attempt to end the independence it had enjoyed under J. Edgar Hoover, who died shortly before the Watergate break-in. FBI officials would have access to the information attributed to Deep Throat and would have a motive for making it public.

“With the benefit of hindsight, it becomes abundantly clear why someone at the FBI would have an interest in leaking information about Watergate to the Washington Post,” Mann wrote in the Atlantic. “In the very first week after the Watergate arrests, FBI investigators found that the White House was putting obstacles in the way of its investigation of the case.”

He went on to theorize that for a senior FBI official, talking about Watergate “was a way to fend off interference with the investigation.” The contacts guaranteed that information developed by the bureau would not be suppressed or altered by Nixon Administration officials, Mann said, and furthered the cause of an independent FBI unfettered by political control.