WASHINGTON -- When Richard M. Nixon died, the current occupants of the White House lost a man that Bill Clinton had once worked to defeat and his wife had once worked to impeach. But Mr. Clinton also lost an adviser, one of the five former presidents he has regularly tapped since he assumed office last year.

The Nixon family and Mr. Nixon's Republican loyalists -- normally no friends of the Clintons -- have expressed gratitude to the president for his private kindnesses and public words. He praised Mr. Nixon Friday night and made his staff available to help with the memorial service, transportation to California, press credentials and the hundreds of other details involved in a presidential funeral.

All presidents pay homage to the office; all presidents quote Jefferson, Lincoln and Roosevelt -- and Bill Clinton is no exception.

What is exceptional is the degree to which this president has cultivated and relied on living ex-presidents.

"These guys have keen minds and a vibrancy," says White House communications director Mark Gearan. "They have a lot to offer."

Before he was inaugurated, Mr. Clinton went to pay his respects to Ronald Reagan. After his election, he has sought the advice of Mr. Nixon on Russia and China and Jimmy Carter on the Middle East and Africa. Gerald R. Ford's counsel was sought on the North American Free Trade Agreement, particularly regarding its impact on Mexico.

The most interesting of these conversations is the one Mr. Clinton had with Mr. Nixon in the Oval Office on March 8, 1993. It was a picture that struck some people -- including partisan young Democratic White House aides -- as being as incongruous as the famous photograph of Elvis Presley presenting then-President Nixon with a handgun.

Mr. Clinton, however, clearly believed that it was politically valuable to be seen with Republican presidents: The White House released the picture of Mr. Nixon and Mr. Clinton, but wouldn't make public one a few weeks later when Mr. Carter visited.

Perhaps more important, the presidency can be a lonely job. Mr. Clinton hinted at this other reason behind his unlikely friendship with Mr. Nixon in the kind remarks he made Friday night in the Rose Garden.

"It's impossible to be in this job," he said, "without feeling a special bond with the people who have gone before."

"The president very much values the opinions of the former presidents because they have particular understanding and insight on certain issues," said White House chief of staff Thomas F. "Mack" McLarty III. "But it's more than that, of course. . . . There's an empathy, a bond -- 'They've walked a mile in my shoes' -- and no one else can really know what that means."

Mr. McLarty coordinated the events involving the former presidents that constituted the most conspicuous use of ex-presidents by a sitting president in recent history:

On Sept. 13, Mr. Clinton presided over the signing of a historic peace accord between Israel and the Palestine Liberation Organization. As Mr. Reagan had done when he rounded up three former presidents for Egyptian President Anwar el Sadat's funeral, Mr. Clinton invited his predecessors to be a part of the history they helped create.

With Mr. Carter and George Bush in attendance at the South Lawn ceremony, Mr. Clinton gave a special salute to Mr. Carter.

Then he added: "Ever since Harry Truman first recognized Israel, every American president -- Democrat and Republican -- has worked for peace between Israel and her neighbors. Now, the efforts of all who have labored before us bring us to this moment . . ."

Mr. Gearan says that making this point was Mr. Clinton's idea. "He's really a student of the presidency," he said. "He's read every presidential biography you can imagine."

The next day, Mr. Bush, Mr. Carter and Mr. Ford all joined Mr. Clinton in the East Room at the signing of the NAFTA side agreements. All three ex-presidents spoke passionately in favor of the agreement. Mr. Bush and Mr. Carter even spent the night in the White House, which they mentioned nostalgically.

The interplay between 1992 opponents Mr. Bush, who negotiated NAFTA, and Mr. Clinton, who helped get it ratified, was intriguing.

"I thought that was a very eloquent statement by Mr. Clinton," Mr. Bush quipped. "Now I understand why he's inside looking out and I'm outside looking in."

There is no particular custom or precedent for how the current occupant of the White House is supposed to deal with previous occupants. Mr. Bush, for instance, rarely sought the counsel of his predecessors. This was especially galling to conservative Republicans who thought that Mr. Bush owed his presence in the White House to Mr. Reagan.

Mr. Reagan himself didn't seem to mind. He sought Mr. Nixon's counsel on foreign policy to a much greater degree than was realized at the time. Mr. Reagan wanted the expertise but apparently wasn't eager to publicize that fact, Mr. Nixon's rehabilitation from Watergate not being as far along as it is today. But in the words of Reaganite Michael Deaver, Mr. Reagan always considered Mr. Nixon "The President."

Presidents Lyndon B. Johnson and John F. Kennedy did the opposite. According to historian Stephen Ambrose, they "made a great show" of consulting with Dwight D. Eisenhower, but primarily because he was so popular and not because they truly valued the old general's advice.

But that, at least, conveyed a modicum of respect.

President Franklin D. Roosevelt did not speak to Herbert Hoover. And, ironically, Mr. Nixon didn't often turn to other presidents. Although he kept Mr. Johnson informed of major decisions, Mr. Ambrose said, Mr. Nixon didn't seek out his advice. In addition, Mr. Ambrose said, "Nixon sure as hell wasn't going to consult with Harry Truman, whom Nixon had once called a traitor."

President Eisenhower also tried to go it alone and only saw Mr. Truman once during his years in office, at the funeral of a man they both revered, George C. Marshall, the World War II general and secretary of state.

Such rivalries have their roots in partisan politics and are not uncommon.

Mr. Nixon, even though he admired Mr. Clinton's skills as a politician, wasn't exactly dreading the thought of hearings into the Whitewater affair, friends say. In his new book to be published posthumously, Mr. Nixon is critical of the Clinton policy on Bosnia and Haiti.

Mr. Reagan got so steamed up by Mr. Clinton's repeated criticism of the 1980s as "a decade of greed" that earlier this year he came back to Washington and gave a speech blistering the younger president.

Mr. Clinton, more than any other recent president, has had more lTC living predecessors both to worry about offending and to turn to for help.

Until the death of Mr. Nixon last week, there were five living ex-presidents compared with just two when Mr. Carter was in the Oval Office.

"This is a very unusual time in history to have this many ex-presidents alive," said Stephen Hess, a leading expert on the presidency and a fellow at the Brookings Institution in Washington. "We have to go back at least a hundred years to find a similar situation." Mr. Hess said that former presidents give a sitting president "a great deal of political protection when a president wishes to involve himself in a foreign policy situation, especially if they're from the opposite party."

Each administration doesn't start anew, he added. "It's like an escalator and you jump on. The legacy of one administration is passed on to the next."

This kind of institutional memory has been helpful to Mr. Clinton, who is not only the youngest president since Mr. Kennedy but who lacked Washington experience before entering the White House.

"He's too young," said Mr. Ambrose, a professor of history at the University of New Orleans and a leading Nixon and Eisenhower biographer. "He needs all the help he can get."

Mr. Ambrose says he wonders if Mr. Clinton's discussions with former presidents are more for show than for really soliciting advice.

It might be some of both, but one thing is for sure: When Mr. Clinton prevailed on the former presidents to call in all their political chits to help pass NAFTA, he got Mr. Carter to do something for another president that Mr. Carter was reputed to dislike doing for himself. He got Jimmy Carter to work the phones in search of votes up on Capitol Hill.