Assemblyman Jerrold Nadler's introduction to politics came when he was 7 years old and his father, "a dyed-in-the-wool Democrat," was a struggling poultry farmer in New Jersey.

"I started becoming politicized when I was growing up because there were two names that were never pronounced except with disdain," recalled Mr. Nadler, who on Wednesday night won the Democratic nomination for Congress from a distinctly urban district that stretches from the Upper West Side to Coney Island.

"One was Dwight D. Eisenhower, and the other was Ezra Taft Benson, his Secretary of Agriculture. I didn't know what they did, but whatever they did made it impossible for chicken farmers to produce eggs without losing money."

Mr. Nadler's father eventually lost the farm, the family decamped to Brooklyn and Mr. Nadler wound up as a student at Columbia University protesting the Vietnam War. Now he is virtually assured of election by his overwhelmingly Democratic constituency, many of whom didn't like Ike either, but today favor free-range chickens, fret about their cholesterol and, he says, "wouldn't know Ezra Taft Benson." Nagging in a Good Cause

But the West Side and its loyal Democratic operatives know the 45-year-old Mr. Nadler. That clearly showed in his easy victory over a crowded field in the Democratic County Committee's convention to nominate a successor to Representative Ted Weiss, who died last week on the eve of his victory in the Democratic primary for a ninth term.

"Jerry is a terrible nudnik," said the Assembly Speaker, Saul Weprin, using the Yiddish term for an indefatigable pest or nag. "But in a good sense. When he has something on his mind that he wants to get done, he'll never leave you alone. I'm sure that from the unfortunate moment that Ted Weiss left us, he was lobbying the county committee."

Or as his East Side colleague, Assemblyman Alexander B. Grannis, put it: "If Jerry has a fault, it's that when he thinks something's important, there is no backing off. He pays a great deal of attention to detail. He knows his subject matter well. He may be a little long-winded; every one of his questions has 16 parts. But he's a very hard worker and I think he'll have a real chance to get something done in Washington."

Such persistence has long been admired in a district that is among the most liberal in the nation, and Mr. Nadler has touched all the right bases, supporting women's rights and gay rights and fighting a steady -- some say, almost obsessive -- battle to increase rail-freight capacity to reduce truck traffic in Manhattan.

Yesterday, as he scurried to television appearances and to meetings with Gov. Bill Clinton and Jewish leaders, and tried to return more than three dozen phone calls of congratulations, Mr. Nadler said he looked forward to continuing the district's liberal traditions in Washington. But he said it was hard to be specific.

"I don't want to say I'm going to be the main pusher on this or that if it's already being done," he said.

Mr. Nadler was raised in an Orthodox Jewish household and schooled in yeshivas until he started Stuyvesant High School. He is the sort of lawmaker who can -- and did -- debate whether Jewish tradition condoned the death penalty, by rattling off memorized passages from the Talmud in Hebrew in a duel with Assemblyman Dov Hikind, a Brooklyn conservative, several years ago.

"It was much to the chagrin of the Assembly stenographer," said Assemblyman Richard N. Gottfried of the West Side, a schoolmate who wrote literature for Mr. Nadler's campaign for Stuyvesant student government president and lost out to him for the Congressional nomination this week after James R. McManus, a fourth-generation scion of Tammany Hall, switched his political club's votes to Mr. Nadler at the last minute.

Among his Albany colleagues, Mr. Nadler is known as much for his breadth as for his depth. To put it plainly, he is a big man, and some of his friends say they worry about his health. Born in Bensonhurst

"It's fine," Mr. Nadler said, adding, "Obviously, I should lose weight. Unfortunately, there's still prejudice on that. It's like racial prejudice or any prejudice. But unfortunately, people still feel they can make jokes on that."

Born in Bensonhurst, Brooklyn on June 13, 1947, in a block that is now part of his district, Mr. Nadler first became active in politics as a student at Columbia in the 60's. He helped organized the effort to deny renomination to President Johnson in 1967 and opposed the war in Vietnam. (His draft status was 4-F, because of an asthmatic condition that still requires him to use an inhaler daily.)

He went to Fordham Law School at night and was elected to the Assembly in 1976. He and his wife, Joyce L. Miller, who supervises low-income housing financing projects for the city's Department of Housing Preservation and Development, have a son, Michael, 7. They live just down the street from Mr. Weiss's family, on West End Avenue at 94th Street.

Mr. Weprin, the Assembly Speaker, had some words of warning for his counterpart in Washington, House Speaker Thomas S. Foley: "There is no member of the Assembly who came to me more often with individual plans and programs. I am going to miss him to that extent. Sometimes I couldn't do what he wanted, but he always made it interesting."

Photo: Assemblyman Jerrold Nadler, with his mother, Miriam, and his wife, Joyce L. Miller, after Mr. Nadler was named the Democratic nominee for Congress as successor to Representative Ted Weiss, who died last week.

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