Even in their hotel meeting room ringed with mirrors, the neo-conservatives of the Democratic Party were but a pale reflection of their once-combative selves.

The image they were striving to project was, as always, that of the ever-feisty, even-partisan Harry Truman. But the foreign policy hard-liners who make up the Coalition for a Democratic Majority have found that their ideological time has come with the election of a conservative Republican president.

And so, at their forum in Washington's Hyatt Regency Hotel this past week, it was clear this Jackson-Moynihan wing of the party now flutters with at least a touch of schizophrenia politica .

On the one hand they want to be true to their Democratic Party traditions; on the other, many are inclined to try to mold their Democratic coalition around Ronald Reagan's White House.

"The situation within the Coalition for a Democratic Majority is extremely fluid," conceded Penn Kemble, president of the Foundation for Democratic Education and one of CDM's leading activits. "There are certainly people in this group of so-called neo-conservatives who went to try to work with the Republicans, and may even be Republicans now."

CDM is one of those Washington organizations that exists mainly on letterheads and deals mainly in influecne. It has no headquarters; it is not into fund-raising. It is an umbrella, a shelter where like-thinking Democrats can marshal forces and test their clout.

Its members are conservative, but they are not the same as those southern conservatives, the traditional conservatives, who call themselves Democrats but who have been giving Reagan his recent congressional victories.

The are instead New Deal/Fair Deal/New Frontier/Great Society Democrats who hold the same foreign policy values that Truman held and think the party has strayed dangerously from the anti-Soviet fold in the years since.

They are called by outsiders "neo-conservatives." Many bristle at that. "We have never moved from the center," proclaims Sen. Daniel Patrick Moynihan (D-N.Y.). "We are the old center of the party."

Criticisms from these Democrats of the Republican administration have so far run the gentle gamut from noncombative to nonexistent. Some do not want to fight because they have switched. Reagan's United Nations ambassador, Jeane Kirkpatrick, comes from the ranks of CDM; so does Assistant Secretary of State Elliott Abrams, Assistant Secretary of Defense Richard Perle and arms control agency director Eugene Rostow.

Others, by the measure of Washington's cogniscenti, have been so quiet that they have seemed to have fallen completely off the radar screen of national politics.

Among their number is the elder statesman of the Democratic hardline, Sen. Henry M. Jackson of Washington.

At lunch the other day, a Soviet diplomat posed a question to an American newspaper editor that bespoke a dilemma not unlike that of a tracking station chief who had just misplaced a Trident submarien.

"Whatever happened to Scoop Jackson?" he asked.

What has happened to Scoop Jackson is in part, that this founding father of the Coalition for a Democratic Majority has found himself more in accord with the foreign policy of the current president than he ever was with that of the last.

Also, after decades in the vanguard of a Democratic-controlled Senate, he has found himself unceremoniously out of power (and, some say, low on spirit) after having nurtured what those close to him say were high hopes of becoming Reagan's secretary of state or secretary of defense.

"Well, it's not really true that I haven't been speaking out," Jackson said in an interview. "I spoke out, for example, on the dangers of leaving synthetic fuels [development] to the marketplace. But I guess that's not news now."

On matters of foreign policy and national security that special interest, Jackson conceded, he is basically "very supportive" of the new tougher tone that Reagan has brought to U.S. policy, including the sharp increases in defense spending and emphasis on combatting internation terrorism.

"Scoop is a little bit undecided about this business of criticizing the Reagan administration," Kimble says. "He has a reasoned relutance to criticize. In a sense, he feels that Reagan's election mandate was due to the same things he has been talking about for years, that the election was a vindication of his ideas."

And so, at the CDM forum, Jackson delivered a speech that had been billed to the organizers of the event as a hard-hitting attack on Reagan foreign policy. It contained two sentences of genuine criticism:

"My thesis today is that the new administration has not yet got its foreign policy act together" and "It strikes me that many fundamental questions have not yet been addressed or resolved," which was followed by a listing of questions about where Reagan's polciy was going but no answers as to what Jackson himself was recommending. These were the nudgings of a Democrat who is 69 years old, who has twice run unsuccessfully for president in long hard compaigns, who must now run for reelection to the Senate in 1982, and who would have much preferred to wind up his long public career as a leading figure in the Reagan Cabinet, according to a number of sources close to him.

This is why, they say, Jackson agreed to serve as a member of the Reagan transition advisory team. Jackson says it isn't so, maintaining he joined the team in a spirit of bipartisanship and that he though all along that it would not be possible for a lifelong Democrat such as himself to find a new home with the Reaganauts.

But others who have talked with him offer a different view.

"Scoop is a doer, and he wanted very much to close out his career as secretary of state or defense," says S. Harrison (Sonny) Dogole, a Philadelphia businessman who has long been close to Jackson and has been one of his prime campaign fund-raisers.

Another prominent Jackson Democrat recalls Jackson having talked of his desire to become Reagan's secretary of state. And a Senate colleague, in talking about how Jackson has not been as outspoken as he used to be, says:

"I think he was kind of hurt by that transition stuff. He went on their team, hoped to become secretary of defense or state and nothing happened. I have a feeling that this led to a certain feeling of depression. That plus the loss of his chairmanships [of the Senate Energy Committee and the Armed Services subcommittee on arms control]. It's understandable."

Moynihan is among those who understands what the loss of a powerful Senate chairmanship means. "You have to have known that glory to miss it," he says.

And puffing himself out to exaggerated proportions, he adds: "I will have you know that you are talking to the former chairman of the subcommittee on water resources. I was big out there in Arizona and New Mexico. I mean, big."

While some of the luminaries of the CDM have jumped to the Reagan team, others are still dedicating themselves to life, liberty and the pursuit of a political majority built around Democrats.

Among them is Ben Wattenberg, CDM's chairman and who says he wants to build from within the party (but also will not say whether he voted for Jimmy Carter or Ronald Reagan in 1980). Wattenberg proposes a three-point plan for a Democratic resconstruction:

"Declare victory," in the name of the national growth that has been accomplished by Democrats the last half-century.

"Declare defeat," by admitting not all liberal programs worked as planned."

"Pick a new fight." Wattenberg says that while Reagan takes the view government is the problem, Democrats can sell it the other way -- that good government is the answer. Democrats can be fiscally responsible while projecting a social conscience, he says.

He proposes that Democrats rally under a new, politically hybrid banner, "Supply-side liberalism," which leaves CDMers searching for a new standard-bearer.

Jackson figures his days of running for president are clearly past, and Moynihan maintains he has no intention of running for president. But he and others of the CDM persuasion serve up a relatively short list of Democrats they say could run with the support of their hardline wing of the party.

Those include Sen. Sam Nunn (Ga.), Sen. John Glenn (Ohio), House Whip Thomas Foley (Wash.) and Sen. Bill Bradley (N.J.). But virtually every time, perhaps surprisingly, the first name mentioned was that of Sen. Gary Hart (Colo.).

Surprising because it is the same Gary Hart who was George McGovern's presidential campaign manager in 1972, moderated now by the passing of time and shifting of issues.

It is not surprising to Moynihan, who is among those who mentioned Hart at the top of his short stack: "Put a man on the Armed Sevices Committee [where Hart is today], let him see the numbers, and then it's not astounding."

But there are those who say they are astounded to find Hart rated so highly by the hardliners. Among them is Gary Hart.

"The said what ?" Hart asked.And when it was repeated he erupted in peals of laughter that were prolonged, if not politic. Regaining his composure and his sense of intraparty diplomacy, Hart elaborated: "Well, I'm flattered."

And asked if he had thought of himself as a Jackson Democrat before, he responded with rhetorical flourish:

"Scoop Jackson and I have disagreed on a number of things. But I don't like to label myself. Label categoris change because circumstances change. And I just find it difficult to position myself on the spectrum, because this is a moving stream."

EPILOGUE: For a while last week, the moving stream had meandered through that meeting room in the Hyatt Regency Hotel just as the leader of the Jackson Democrats was treating himself to a quick toe dip in the name of two-party politics. Later, an interviewer observed to Scoop Jackson that he had seemed to find it difficult to bring himself to make even mild-mannered criticisms of Reagan foreign policy.

"I wasn't condemnatory," he conceded. "It was just a little prodding on my part to stir them up. It comes from someone who is very supportive." He paused, then added:

"But I am not a sycophant."