The most famous quote from the Watergate era was surely that question posed repeatedly during televised hearings by Senator Howard Baker, the Republican vice-chairman of the official Senate committee investigating the scandal.

In an effort to discover what part President Nixon played in attempts at a cover up, he insisted the crucial issue was: "What did the president know, and when did he know it?"

Certainly, I've never forgotten it. And as this Clinton scandal has unfolded, the first part of that question has seemed to me to be just as relevant albeit for a very different reason.

Initially Nixon denied any involvement

The answer, of course, is that Mr Clinton knew precisely what had happened between him and Monica Lewinsky, and with everyone else involved too. And yet, he never learned the lessons of Watergate. For more than two years, President Nixon had stubbornly refused to concede defeat, firmly believing he could prevent the truth becoming public property.

He was proved wrong and the price was his resignation. Now the historians agree that had he come clean at the start, he could have survived virtually intact.

Clinton's tribute following the death of President Nixon

This week in the United States, the commentators are saying the same about Bill Clinton and noting that compared to the sins of Watergate, his are much less serious. But he chose the failed Nixon tactics.

Making this situation more incomprehensible is the fact that whereas Richard Nixon was facing accusations from reporters, Mr Clinton has been up against the independent counsel Kenneth Starr. The press had no official backing, but this man has had massive legal power. Even so, Bill Clinton still believed he could win.

Both presidents castigated the press in their bid to win public support and sympathy, and Mr Clinton has done this with far more success. That is probably because his main transgression was one of a sexual nature, with the average American far more understanding about the need to lie about it.

Dirty tricks: The Watergate break in

Anyway, as a sequel to Watergate, the Clinton scandal cannot hope to compete. Sex may have been an ingredient noticeably absent from Watergate, but there is no suggestion of secret tape recordings in the Oval Office, and no buggings, bribes or break-ins.

And while it is still the president of the United States playing the central role, now the cast of supporting characters is both smaller and less important.

Watergate involved the most senior of White House staff, the attorney-general, and a host of others who wielded the kind of power which kept America going. They were seen then as the "untouchables", far too influential to have to worry about the investigations of a few journalists. And when it came to credibility, the word of a reporter - even one working for the much-respected Washington Post - stood no chance against those of a president and his closest aides.

But what kept Watergate going and the population enthralled was the steady stream of sensational revelations over such a long period. Each seemed more amazing than the last and I remember only too well reporting again and again how Americans simply could not believe what they were being told.

That has been another of the major differences. Watergate was a series of damning disclosures, each backed up by so much evidence that Mr Nixon and his colleagues could be witnessed sinking deeper into trouble on an almost daily basis.

Not so in the case of Bill Clinton. Even in "sieve city" as we came to know Washington because of its constant leaks, the accusations against him had remained unsubstantiated in public because the evidence was heard in secret by a grand jury.

Clinton: Following in Nixon's footsteps?

And there was not the same public thirst for the chase. This president's popularity stayed high despite the scandal, probably because America had grown stronger under his rule with a change of leadership threatening that success.

For me, this time allowed the freedom of an opinion because reporting the story was not my assignment, I have long believed Bill Clinton was concealing the truth.

The turning point came with the realisation of Kenneth Starr's determination to pursue Monica Lewinsky's "real story" - even though finalising a deal on immunity from prosecution took several more weeks.

This was not a man delving in the darkness hoping to strike lucky. He knew what he was after and knew it was out there.