I HAD LUNCH WITH President Clinton recently. Well, not quite. I was at the counter of a pizza parlor next door to my office, wolfing down a slice to the accompaniment of the restaurant's television set, which was tuned to cable news.

Clinton was on the screen, but his voice was inaudible in the bedlam of the restaurant. He was addressing the National Farmers' Union and saying something about providing emergency financing to farmers.I was more interested in the television image: the president's handsome head bobbing and weaving from side to side, the picture of a cheerful, vigorous, buoyantly confident man. It seemed surreal. This man is in trouble? You can't be serious.

Clinton is, of course, in the deepest trouble, sliding steadily toward impeachment proceedings. It is impossible to know whether he will dig himself out, how long the drama will drag on and what effect the distractions and anxieties of the gathering storm may have on the nation's business. I have seen the process before - as counsel to Richard Nixon in 1973 and 1974 during the decline and fall of his presidency.

The course of the Nixon administration's dissolution after the Watergate break-in was nasty, brutish and very long. During Nixon's last two years in office, he suffered the forced resignations of his principal aides, Bob Haldeman and John Ehrlichman; the conviction of John Mitchell, his friend, law partner, attorney general and campaign chief; the discovery and release of the humiliating and incriminating White House tapes, and the forced resignation of his vice president.

These blows left Nixon desperately wounded, yet he considered the prospect of leaving the presidency before finishing his term an unacceptable shame. Even after impeachment was inevitable, Nixon struggled to survive in the only life he considered worth living. For the last year of his presidency he was imprisoned, psychologically and politically, in Watergate.

Yet the world did not stand still. This was a time of international change and crisis. There was detente to be implemented, China to be opened, a Vietnam peace to be maintained. In 1973, the Middle East erupted in war and there was an Arab oil boycott, which rocked the world economy.

Watergate severely diminished Nixon's ability to deal with these crises. It virtually destroyed the prestige and power of his presidency. By 1974, his standing among foreign leaders, once pre-eminent, was reduced to a pantomime of cer-emonial courtesies.

The historic foreign policy structure that Nixon and his national security adviser, Henry Kissinger, had painstakingly assembled during their first term became a hollow shell. The fragile peace in Vietnam soon collapsed.

Watergate also depleted Nixon's energy and distorted his judgment. Monica Crowley, whose biography, "Nixon in Winter," chronicles the former president's last years, says he repeatedly told her that his judgment was "off" as a consequence of his bitter and exhausting effort to survive.

The night Nixon called me to the White House after midnight, simply to hear a long, furious denunciation of a leak of one of his tapes, epitomized his distraction from his Presidential duties. Watergate was the order of the day every day until the end.

Clinton and his senior political advisers are alert students of presidential history, yet he seems determined to ignore the scandals and hammer away at national issues, raise campaign money and rally his political supporters.

A newcomer to national attention, Chaka Fattah, a black Democratic representative from Pennsylvania, is arguing on many cable news shows that the impeachment of President Clinton could cause the loss of two to four million American jobs, a burden that would be visited disproportionately on African-Americans and the poor. In a show of forensic chutzpah, Fattah supported this thesis by asserting that Nixon's resignation caused a similar rise in unemployment.

Will Clinton's strategy work? This president has the advantage of job approval ratings higher than Nixon enjoyed and an economy that is more robust. Clinton has the added asset of a temperament far different from Nixon's.

Nixon could not lie without betraying acute embarrassment; Clinton is - well, different. Nixon brought to the presidential office a collection of angers and resentments that seriously distorted his political calculations. Clinton bears fewer of these deforming wounds.

Still, over time, it is certain that the pressures will take their toll, even on a president as sturdy as Clinton. For this reason, the country has to begin an orderly process for resolution of the charges against him. We cannot achieve closure overnight. Some congressmen, pundits and editorial writers have begun to call for the president's resignation - but that, in Nixon's immortal words, would be wrong. The country is not yet ready for such a trauma.

The constitutional process should go forward, and though this formula may seem like a conventional piety, it is not. The impeachment process - the consideration, the hearings, the drafting of impeachment articles, the debate and vote - take time, and that time is needed for the country to consider its options.

This purgatory will impose painful human costs, but they can be borne. The other night I ran into a member of a major regulatory commission, a supporter of the president and the first lady since their first national campaign. He was dismayed by the current mess. "What would you do?" he asked me.

"No anguished press conferences," I said without hesitation. "No resignations on principle. Just keep working."

I was surprised at my swift certainty. But, then, I've been there. As Watergate's clouds gathered and swelled over the Nixon administration, people on the inside had to decide each day whether to keep working or to detach themselves from their jobs and from the president. His problems increased the nation's problems, which was all the more reason that those of us who chose to stay and cope never regretted it.