Hubert H. Humphrey, the most exuberant of American politicians and by the time of his death surely the most beloved, was brought back to the Capitol for the last time yesterday for the sort of national tribute normally reserved for heads of state.

His body lay in state in the Capitol Rotunda, resting upon the same catafalque that bore Lincoln and Kennedy and other Americn leaders, while around his flag-draped casket moved long lines of his fellow citizens.

The doors of the Capital will remain open until 10:20 this morning to permit the public to pay its respects. Then, at 11, a congressional ceremony will begin. It will be attended by President Carter and other leaders. Also scheduled to be in attendance is Richard M. Nixon, who will be returning to Washington for the first time since he was driven from office in disgrace.

It was Nixon's eyelash victory - the margin was less than 0.1 per cent - that denied Humphrey the presidency in the embittered year of 1968.

Humphrey's body will be flown back to his native Minnesota for more solemn tributes this afternoon. His funeral will be at 3 p.m. (Washington time) Monday in Minneapolis.

The scene at the Capitol yesterday was familiar, and normally one associated with sudden tragedy and national grief. Humphrey's final tribute is different in that his death was not expected and both he and his friends had tried to avoid any show of undue sorrow.

"He would have us remember him with joy and not in mourning," his political protege and fellow Minnesotan, Vice President Mondale, said upon announcing Humphrey's death.

Mondale was waiting at Andrew's Air Force Base when Humphrey's body was brought back to Washington from Minnesota yesterday morning. President Carter had dispatched Air Force One to Minneapolis for Humphrey's final trip to the nation's capital, a city he had known as well over the last 30 years of public service.

The plane was one of many reminders of Hubert Horatio Humphrey's association with the great events of American life for more than a generation. It was the same one that had carried back the bodies of John F. Kennedy, who Humphrey had competed against for the presidency, Johnson, whom he had served for four turbulent years as Vice President.

Humphrey's death, of inoperable cancer, had come at 10:25 p.m. (Washington time) Friday night while the senator lay in a coma at his lakeside home in Waverly, Minn., about 40 miles west of Minneapolis. He was 66.

At his bedside were his wife, Muriel, their three sons, Hubert III (Skip), Robert and Douglas, and their daughter, Nancy Solomon. The Humphrey family flew back with the body on Air Force One.

Then, after a 19-gun salute, they entered limousines and left in a motorcade for the Capitol.

It was 11:50 a.m. when they - and the hearse - arrived at the Capitol Plaza grounds. The pavement was glistening from a light rain, and thick, gray clouds scudded over the Capitol dome. Around the Capitol, workers were busy shoveling away the remnants of a 4-inch snow that graced the city Friday.

The sound of a rifle volley echoing off the government buildings on Capitol Hill blended with the sound of a band playing the strains of "Faith of Our Fathers" and "A mighty Fortress Is Our God" as Humphrey's casket was carried slowly up the steps and into the Rotunda. An honor guard stood stiffly at salute on the same steps where Humphrye had watched so many Presidents be inaugurated, and where he had taken his vice presidential oath exactly 13 years ago this week.

For the next hour, the Rotunda was closed to the public as members of the senator's family and then his colleagues in House and Senate paid their respects. Then, at 1 p.m. the doors were opened and citizens began filing slowly past the bier.

As Humphrey's body was brought into the Capitol, tributes to his longicareer poured in from around the world. A common theme was the nature of his character more than the quality of his political works.

"A good and noble man," Sen. Edward W. Brooke (R-Mass.) called him, in words repeated by others. "A noble American has been taken from us," said his longtime Senate colleague Jacob K. Javits (R-N.Y.).

Joseph A. Califano, Jr. Secretary of Health, Education and Welfare, who had worked with Humphrey during the Johnson White House years and in Democratic politics since, said:

"I cannot imagine American politics without his astounding and boundless humanity, and I am deeply grateful to have served in government with the man whose great stature stemmed from his uncanny ability to express - and then meet through creative leadership - the needs and aspirations of the individual citizens of this nation."

One other tribute evoked Humphrey's long association with liberal Democratic causes. It came from Joseph L. Rauh Jr., vice president of Americans for Democratic Action.

"Hubert Humphrey's life is a lesson to practical politicians in liberal idealism," he said, "but it is also a lesson to liberal idealists in practical politics."

But it was not as a liberal, nor as an ideologue, that Hubert Humphrey was being remembered. The grace with which he had handled his political defeats and the warmth and goodwill he exuded won him an effectionate place in American hearts. But it was his quality of quiet courage and uncomplaining humor in the face of his fatal bout with cancer that clearly touched the national spirit.

Humphrey had left Washington for the last time just before Christmas, and had hoped to return this week for the opening of a Congress in which he had played an increasingly influential role. Even as he was visibly failing, he retained a self-deprecating sense of humour about his condition.

"You can cut back on the funeral arrangements," he told an aide during his last days in Minnesota, "because all the eulogies already have been delivered."

One of the eulogies he would have liked came from another erstwhile political opponent, Jimmy Carter.

The President, in part, had this to say:

"For 30 years, his voice was heard from one end of this country to the other - most often in defense of the oppressed, the hungry, the victims of poverty and discrimination. All of us will miss that voice. It was as familiar to Americans as the voice of a member of their family. And, in a sense, Hubert Humphrey was a member of every family in America.

"Hubert Humphrey was a fundamentally happy man, a man who really did love his fellow human beings and, in victory and in defeat, he set an example of generosity, sincerity and hope.

"The only thing more courageous than the way in which he led his life was the manner in which he left it."

Humphrey's body will also lie in state in the Rotunda of the Minnesota Capitol in St. Paul Monday. His funeral service will be at the House of Hope Presbyterian Church in St. Paul, with burial in Lakewood Cemetery, Minneapolis.