A COOL summer night in New York City, August 1976. Jimmy Carter swept into Madison Square Garden to make his acceptance speech and a new era was born; the throng cheered its leader as the convention came to a close, then headed for the waiting cabs and late night parties.

It was just before 1 a.m. when the limousine pulled up before swank Maxwell's Plum. The familiar figure got out and strode towards the maitre d'. He was told the restaurant was closing. "But Muriel and I just want a bite to eat," he said. A bored look around the still-filled premises and a bored reply: "I'm sorry we're about to close." In a moment the car was speeding off into the night, its two solitary passengers disappearing behind the tinted glass.

Hubert Humphrey's quest for the presidency was finally, unquestionably over. In April, he had said he wasn't running but that night, after nominating his protege, Walter Mondale, for vice-president and blessing the ticket--the message was finally sinking in. It was all over. In two months would come cancer surgery and the beginning of a long fight destined to leave him without much chance even to view as an observer the presidential politics of the post-Humphrey years.

Yet for all that, Humphrey didn't end up the embittered man so many others would have become. His dying, like his living, was done in public. It was characterized by the same boundless optimism that animated his life in politics. In the last several months one came to realize that the "politics of joy" he preached were a little less corny than many would have cared to admit a few years ago, his zestful public spirit a little more affecting.

The early career, of course, was an impressive one: his legislative efforts helped bring the nation civil rights bills, the Peace Corps, Food for Peace, better social security, a nuclear test ban treaty and improved health care, to mention only a few achievements. Humphrey was the quintessential New Deal liberal and that was important during these years, the years when the government recognized its obligation to expand its responsiveness to human needs. Someone had to push the Senate in new directions, fight the good fight--and more often than not it was Humphrey, a "giver" in the fullest sense, who took it on himself to do so.

Unfortunately for Humphrey--and for the world--that impression cannot stand alone. The war happened, and if the intensity of the sympathetic outpouring of recent months suggests he left few if any enemies among politicians when he died, the question of whether anti-war liberals will eventually forgive him remains unanswered.

The political mistake of waiting until the Salt Lake City speech of October, 1968 before publicly separating himself from LBJ's war policies is indisputable and something Humphrey readily admitted to later. It is the larger question that will continue to stir debate: assuming Humphrey thought he had to support Johnson to win, was he justified in reversing Henry Clay's dictum--in deciding he'd rather be President than right--for the purpose of putting himself instead of Richard Nixon in office?

In some ways, those who take a hard-line on Humphrey's career are persuasive. His position on Vietnam was no small blot on an otherwise brilliant record--to the contrary, attitudes on the war must be considered central in the assessment of anyone who held high office during those years. Humphrey may not have been an architect of the war policy but in playing the role of supporter he implicated himself in some of its ugliest facets: fudging reports of fact-finding trips, referring to "our finest hour," condoning the clubbings in the streets of Chicago.

EVEN SO, it cannot now be argued, as the Left did in 1968, that the choice between Humphrey and Nixon was an irrelevant one. That lesson has been learned in the most painful way imaginable, particularly by the poor and disadvantaged who depended for survival on the kind of compassion Humphrey exemplified,

Moreover, once out from under the imposing shadow of Lyndon Johnson, Humphrey probably would have ended the war. In private he began to turn around relatively early. As a result of a 1965 memo he wrote to LBJ--unreleased until 1976--he was frozen out of the Administration's decision-making process. The memo read in part:

It is hard to justify dramatic 150-plane U.S. air bombardments across a border as a response to camouflaged, often non-sensational, elusive small scale terror which has been going on for ten years in what looks largely like a civil war in the South....

It (escalation) will underwrite all the negativism and disillusionism which we already have about foreign involvement generally--with serious and direct effect for...AID, United Nations arms control, and socially humane and constructive policies generally.

For these reasons the decisions now being made on Vietnam will affect the future of this Administration fundamentally. I intend to support the Administration whatever the President's decisions. But these are my views.

IT WAS the pledge of support that proved to be Humphrey's undoing in 1968. By defining the vice-presidency in terms to loyalty to the president, he precluded the exhibition of courage required of him and for far too long advocated an immoral war against his better judgment.

But in the final analysis, all one can really do when assessing a politician is to measure his contributions against his shortcomings. On that account, the pharmacist's son-turned-statesman comes out deserving of the veneration he has been accorded. When historians decide, as is their wont, which men can be called "great"--which combine consistent articulation of ideals with a constructive and inspiring approach to the conduct of public affairs, Hubert Humphrey will justifiably be among them.