BACK HOME the ADA was never like this. You expect staunch liberals, oldish, straight-backed, and supremely moralistic. And so you are surprised when you step into the gilded ballroom of the Sheraton Plaza Hotel and find 800 Americans for Democratic Action-young and fashionably dressed-minis, midis, maxis, and even a pair of hot pants. Paying $1250 a plate for dinner, they are at least reasonably well off, and their clothes suggest that they are even better off than that. The guest list is heavily studded with Jewish names, but it also includes a few McKay's and O'Connell's and even a Saltonstall. The guests at the head table represent Mass Pax, the NAACP, the UFW, the UAW, and an Afro-American arts center. Still, you wonder, beneath their mod exterior, how different are these Boston liberals from the older, straight-backed stereotypes?

And you ask yourself, what does it mean to be a liberal? In Boston it means Drinan, Dukakis, and Harrington; playing politics within the system-unlike the radicals-but always demonstrating your social concern. Being a liberal is a self-conscious awareness. It means seating two blacks at the head table when there are only a handful of their brothers among the 300 paying guests. It means not eating your salad until someone announces that it is made from Union lettuce. It means hissing sexist speakers. Or, as the post- Love Story joke goes, being a liberal means always having to say you're sorry.

The apologies come in the form of involvement and support-financial support especially, for money is one thing these people do have (and probably is why they think they need to apologize). With an obvious humility they depend on others, more militant and more deeply involved, to identify the causes worthy of their concern. Perhaps, then, being a liberal means willingly isolating yourself from most of the ugly social problems-salving your conscience but still keeping your distance by inviting into your homes and ballrooms certain select, cleaned-up representatives of the angry peoples of the world.

If so, then Harold Hughes-once a truck driver, a reformed alcoholic, and now the dove senator from Iowa and unannounced Presidential hopeful-brought it home to Boston liberals last Saturday night at their Roosevelt Day dinner.

FIRST COME the preliminaries, in which the Boston liberals prove themselves to Hughes: the guests pat each other on the back for Father Drinan's Congressional victory, and they assure Dukakis that they still love him, despite his defeat. At last, Hughes lumbers to the podium. As he stands you realize for the first time that he is a huge man, and for a moment you see him as a truck driver come to talk straight to these college-educated, refined suburbanites. But his deep voice quickly launches into a joke about Nixon and dispels the truck driver image. Once and for all, you know that the man is Harold, not Howard, Hughes.

The joke is important, because Hughes takes it from an article in the New York Times. He is telling his sophisticated Boston audience at the start that he, an Iowa man, can speak their language. Hughes' oratorical reputation pictures him as a revivalist minister, but for the moment he submerges that image in order to draw in his listeners. Accordingly, he begins with the war. Laos is to China as Mexico is to the United States, he says, and how would we feel if enemy troops were stationed in Canada?

Trying to identify the source of the evil in the country, he returns to Nixon and his inaugural pledge to "bring us together." Hughes is still playing with the audience as he delivers his next line like Orson Welles: "And then they sent forth into the country the Vice President." He accuses Nixon of deliberately breaking apart the country after pledging conciliation. "The teeth still show despite the olive branch," he says, his anger beginning to show for the first time.

NOW HUGHES is building up to the heart of his argument. He cites the divisions between occupational, racial, ethnic, and age groups, wondering why they haven't been pulled together by common opposition to the war. His reading of the country is optimistic, for he suggests a widespread sentiment for peace. In fear and disillusionment, he explains. Americans are reaching out for symbols: laborers take the flag while students opt for change, and neither group understands the other. "Are the walls between these groups real or are they illusory?" he asks. "They are real in the sense that they exist. They are illusory in the sense that they have no reason to exist."

Hughes is even optimistic enough to see the seeds of unity in Iowa, where hard-hats, farmers, and students recently joined together in a demonstration against Nixon. "The President had finally succeeded in bring them together," he says seriously.

Now Hughes has the crowd with him, and he announces his solution: "What this nation needs more than anything else is a new era of forgiveness and reconciliation." It's an old idea, Whitmanesque and almost corny. Yet, Hughes firmly believes it, and from it at last he can slip comfortably into his gospel preacher role. He begins to speak of the Divine Creator and the gospel of education, anti-hunger, and equality. There, in the Sheraton Plaza, of all places, a religious movement is being built.

But to see Harold Hughes only at this level would be to miss the real meaning of his message. Although couched in religious terms, what he is proposing is a community of all Americans, a united nation poised for action. It sounds like Bobby Kennedy's appeal to minorities, but Hughes' coalition is even more broadly based; it includes laborers, students, blacks, ethnics, the aged, and anyone else who will join him. You sense that Hughes knows these people. He need not create a sympathy, because he instinctively feels one. It is perhaps only the students and the refined Boston liberals who do not come to him naturally. With these groups he depends on common goals and hopes that they will support him.

As he ends his message Hughes asks only "that we learn to love one another." He finishes speaking, and the crowd gives him a standing ovation. Whether or not they, the money people, will buy his message remains to be seen. And it also remains to be seen if Harold Hughes is the man who can lead us into this great love.