New-style Democrats poised to lead. Sen. Kennedy's decision to sit out the '88 presidential race will alter tenor of campaign for both major parties

A new generation of leadership is now poised to take over the Democratic Party. Sen. Edward M. Kennedy of Massachusetts, who announced last week that he would not seek the Democratic presidential nomination in 1988, was seen as the heir of past Democratic greatness -- the New Deal of Franklin D. Roosevelt, the Fair Deal of Harry S. Truman, the New Frontier of John F. Kennedy, the Great Society of Lyndon B. Johnson.

Now, Senator Kennedy's surprise announcement throws the contest wide open to as many as a dozen potential candidates within his own party, and makes Sen. Gary Hart of Colorado the instant front-runner for the Democratic nomination. Kennedy's decision changes the tenor of the '88 race in important ways for Republicans as well.

The Democratic Party, as defined by Kennedy, is a champion of the poor, the hungry, the jobless, and the minorities. It reflects policies that were put in place when America had an economy unchallenged in the world.

New-style Democrats such as Senator Hart, Gov. Bruce Babbitt of Arizona, Rep. Richard A. Gephardt of Missouri, and Sen. Joseph R. Biden Jr. of Delaware have other, additional priorities. They wrestle with questions of military reform, industrial policy, foreign competition, tax reform, and technological innovation. Their appeal is less emotional and more businesslike.

Kennedy's decision also opens the way for another potential candidate who represents more traditional Democratic values: Gov. Mario Cuomo of New York. Kennedy has singled out Governor Cuomo as a ``very strong candidate'' for the party nomination.

The Kennedy decision surprised official Washington and raised the question, Why? The senator explained: ``I have decided that the best way to advance the values that you and I share -- peace on Earth, economic growth at home, compassion to all Americans -- is to be a United States senator and not a candidate for president of the United States. I know that this decision means that I may never be president, but the pursuit of the presidency is not my life. Public service is.''

In a brief news conference in Boston Friday morning, Kennedy said that speculation about his presidential plans has made him ``unable to speak to the issues of importance to me and the American people.''

``People are no longer interested in the substance of what I'm saying,'' he said. He added that they seem more concerned about whether he's leaning left or right and whether he is losing or gaining weight.

Sources close to the senator said Kennedy was concerned that every word, every decision, every move he made would be given a political spin by the press if he stayed in the 1988 race. Kennedy felt that is what happened when he traveled earlier this year to South Africa and when he supported the Gramm-Rudman budget bill and the line-item veto.

Even so, Kennedy clearly gives up a genuine opportunity. A recent Republican Party poll by Robert Teeter found that Kennedy remains the most popular Democrat. Some 44 percent of the voters polled supported Kennedy for the Democratic presidential nomination -- double the 22 percent for his nearest rival, Senator Hart. In a trial heat between Kennedy and Vice-President George Bush (the front-running Republican for '88), Mr. Bush led, but only 51 percent to 45 percent, according to the poll.

Kennedy's principal strength, the poll showed, was among voters in four categories: low income, Jewish, Hispanic, and black. In contrast, the same poll showed new-style Democrat Hart losing the Hispanic vote to Bush, but running better than Kennedy among upper and middle-income voters and the young and better educated.

Kennedy's withdrawal could be bad news for Republicans. It gives new-generation Democrats a clear shot at the top of the party's ticket in 1988. And that could threaten recent Republican gains.

The recent GOP resurgence has been led by young, middle-class voters for whom the key issues are taxes and jobs. Foreign competition and the decline of basic US industries have caused great stresses throughout the American economy, and this has played into Republican hands. The GOP successfully branded Democrats and their nominee in 1984, Walter Mondale, as out of touch and wedded to old policies of ``tax and tax and spend and spend.'' The label doesn't fit so neatly with the new-style, high-tech Democr ats in Congress.