Sylvia (it used to be Sima) Cohen was on a sentimental journey. Certainly politics was the farthest thing from her mind. But what she had to say, and where she was visiting, were marvelously pertinent to the predicament the Democrats find themselves in. Even more, her story adds a missing dimension to the heavy maneuvering going on uptown as the delegates prepare to convene. Politics, after all, is supposed to be about people, and Sylvia Cohen could tell the hard-eyed pros some things they seem to have forgotten.

On the lower East Side today the names on the stores read Figaro and Morales instead of their Jewish and Italian antecedents, but the scene remains depressingly the same -- garbage and debris fill the streets, some still covered with cobblestones, and derelicts huddle in the doorways and alleys. Efforts to eliminate this visible symbol of urban poverty have been a notable failure. On the old brick walls throughout the area are posters depicting a large broom and the slogan "Clean Sweep." A message implores citizens to beautify their neighborhoods. Many of the posters stand, with unintentional irony, next to others hung by the city: "CAUTION," these read, "children, animals, this area has been exterminated by the Bureau for Pest Control." All of the messages, whether of hope or warning, are covered with unintelligible graffiti -- a fitting gesture of the people's contempt for the politicians who keep promising change and a better tomorrow.

The narrow streets and the tenements comprising the Lower East Side have witnessed wave after wave of people struggling to escape the harshness of that environment.

In recent years, romantic mythology has created a sentimental and false aura about this section of old New York; Jacob Riis' great work of nearly a century ago, "How the Other Half Lives," describes the brutal realities of life there. If anything, the picture today appears more bleak. It's as if the struggle to escape has ceased and the hope for finding the better life that sustained those earlier occupants has vanished. Walking the streets now provides evidence of a segment of society that has learned to acept the unacceptable.

Not all of the streets, though. On East 11th, not far from the river and just off Avenue B, police barricades have been set up around one small block. Blacks and Puerto Ricans stand outside the barriers, gazing on a scene that springs out of the past.

The pavement has been covered with dirt and straw, laundry dangles on lines strung overhead from building to building, the storefronts have been refurbished, women in long cotton gowns carry bags of laundry. Policemen in English-style bobby hats and long blue coats amble by on patrol while merchants tend pushcarts laden with vegetables and household wares, and horses pull wagons filled with straw and hardware. The signs on the store windows are written in Hebrew and the names are Moishel, shipper of coal, and Dworetzky & Shlefrein. No graffiti cover these storefronts; the signs offer poultry, butter, eggs, woolens, violins and sheet music.

And there, a few feet inside the barriers, transfixed by this portrait of another world, was Sylvia Cohen. "Why do you think I'm here?" she said. "I had to come."

The moviemakers had transformed that one block into a set for the film, "Ragtime," based on the book of that name about immigrants' life on the Lower East Side in the 1890s. In a literal sense, it was Sylvia Cohen's life that was being depicted. She was born there, and although she moved out of Manhattan some 40 years ago, her roots go back to that Lower East Side street.

"My mother was pregnant with her third child when my father came here from Russia to make his fortune," she was saying. "His name was Sam Gold when he became a citizen. Before that it used to be Golick. He started as a laundry worker here.

"Later he opened his own laundry. He took in relatives, who also came over then, as boarders and when he had saved enough money he sent for my mother. I was the first one of the rest of the children born here."

She grew up in the neighborhood, went to the public school, worked as a bookkeeper in the garment industry, then many years in the New York City civil service, married, raised two sons, and now, a widow, lives alone off Pelham Parkway in the Bronx. Life had never been easy. She remembers problems of anti-semitism, of her parents being roughed up by other immigrant groups -- Irish and Germans -- because they were Jews and "talked different," of herself having to learn to fight, and of the bitter despair of the Depression.

But there never was a time that she didn't have a strong sense of pride in America and of the promise of the future. "I love our country," she was saying, "and I'm grateful to my parents that they came over here."

Now, though, she finds herself deeply disturbed by conditions in the country and what she sees as a failure of political leadership. As a Democrat, worshipper of Franklin Roosevelt, she's particularly upset at the presidential prospects her party now offers.

"I don't even know who to vote for," she said, "and I'm a good citizen. But I feel very unhappy. I don't even know who to trust. I feel that I don't particularly care for Reagan. I never even liked him as an actor. I feel he's sort of a reactionary, and I'm worried about what I see as a revival of hatred running in the country, all this fundamentalism and the rise of the Ku Klux Klan. It bodes very ill. That's my opinion, just mine.

"But Carter, I think he's made so many mistakes, so many blunders. I almost feel sorry for him. I feel sorry for his brother. What a family! On Monday night he said he's not his brother's keeper and that they love each other, and I think he said his brother doesn't tell him how to run the country and he doesn't tell him how to run his life.

"I don't think Carter is a dishonest person. I don't think he's a thief. But I think he's not to bright. I think his wife is the brighter one. So I am disappointed in him because I voted for him last time.

"And Kennedy, never, never. I have no interest in him ever. I liked John Kennedy, but I never could go for this one."

As for John Anderson: "He's the one who proposed establishing christianity as a national religion. He's the worst."

She became somewhat indignant at the suggestion that she might not vote at all. "I always vote," she said. "Here is what I will do. "I will talk to myself and say, 'What are the lessons, what do we know about them,' and which is the lesser of the evils. That is what I will tell myself before I vote." i