MANCHESTER, N.H. -- You could call it the "greening" of a moderate. Or you could, as some of his southern supporters do, cuss it as the seduction of a centrist by the siren calls of the left that lure Democratic presidential hopefuls as they campaign in Iowa and New Hampshire.

But whatever the description, what has been happening with Rep. Richard A. Gephardt (D-Mo.) in the last few months typifies a central Democratic Party problem. With the declaration of noncandidacy last week by Sen. Sam Nunn (D-Ga.), the Democrats again confront the question of whether any of their contenders can satisfy the "litmus-test" liberal constituencies in the early contests and still compete effectively for votes in the more conservative states of the Old Confederacy.

It is a challenge for all eight of the avowed or undeclared Democratic contenders, but none feels it more acutely than Gephardt. He has more public endorsements from southern Democratic elected officials -- including large numbers of House colleagues from Florida, Texas, the Carolinas and the Gulf states -- than anyone else in the race.

His campaign manager, South Carolinian William Carrick, said in an interview that the basic strategy of the Gephardt campaign is "to do a Carter" -- to squeeze out an early plurality victory by incessant campaigning in Iowa and New Hampshire and then go South for the March 8 super primary "as one of the less liberal candidates" still in the race.

In an interview here Thursday, before he started a brief family vacation, Gephardt said, "If you need a label for me, moderate is as good as any." His 10-year record in the House bears that out.

Former Democratic national chairman Robert S. Strauss, a Texan, helped him gain a rare freshman seat on the Ways and Means Committee. The late Rep. Gillis Long of Louisiana made Gephardt his protege and successor as chairman of the House Democratic Caucus.

Interviews with colleagues on the Ways and Means Committee and the Budget Committee support Gephardt's assessment of himself: "What I try to do in approaching issues is to do it from a practical point of view, to ask what will solve a particular problem. I have strong beliefs about things -- arms control, Central American policy, tax reform, trade, health care, Social Security and what have you -- but I don't come to those from an ideological viewpoint. I try to look at the facts of a particular issue."

As a legislator, Gephardt is known to his colleagues for his patience in listening to conflicting views and his creativity in finding compromises to resolve them. His home district, a suburban St. Louis area of blue-collar voters with conservative social views, is a mixture of northern and Dixie influences.

In his first six years in the House, Gephardt more than once defied the wishes of liberal lobbies. At various times, he opposed raising the minimum wage and increasing the mandatory retirement age, creating the Education Department, an independent Consumer Protection Agency, community mental health centers and shelters for battered women. He voted against extending the deadline for ratification of the Equal Rights Amendment and against a major expansion of the national park system. He has, at times, supported tuition tax credits and an antibusing amendment to the Constitution.

It is hardly the profile of a stereotypical liberal, and at times when the mood of Congress and the country has swung in a conservative direction, Gephardt has moved with it.

Congressional Quarterly's roll-call analysis shows that Gephardt joined the "conservative coalition" of southern Democrats and Republicans more often than he opposed it in the first two years of the Reagan administration. From 1983 onward, he has more often opposed than supported that coalition, voting more like the typical northern Democrat and less like the typical southern Democrat he resembled in the early 1980s.

In 1981-82, he voted for such Reagan initiatives as the tax cut (after the Democratic alternative, which he favored, went down), the MX missile and the B1 bomber -- positions for which he has been criticized by such liberal rivals as Massachusetts Gov. Michael S. Dukakis.

Gephardt said, "I don't remember any change of opinion or feeling between 1981 and 1983" that would account for the shift in the CQ {Congressional Quarterly} scores. Michael R. Wessel, the top aide on his House staff, said that in those years he saw Gephardt becoming "more disillusioned with the Reagan initiatives as he recognized Reagan was not willing to compromise or accommodate Democratic views. And as he became more of a participant in the Democratic leadership process, he felt more of an obligation to support its positions."

Since he began his national campaign, Gephardt has taken a number of stands that have brought him closer to activist constituencies in the liberal wing of his party.

The most celebrated shift involves his position on abortion. In 1985, Gephardt recanted his previous support for an antiabortion amendment to the Constitution, saying that the protracted controversy over the amendment had clouded prospects of building support for programs that offer "alternatives to abortion." At a news conference at the convention of the National Women's Political Caucus last weekend, he confirmed reports that while he would not vote in the House for federal funding of abortions, he now has pledged not to veto any such appropriations as president and not to seek modification of the Democratic platform endorsing such funds.

In trade, he has become the principal advocate of an amendment bearing his name, which would require retaliation, under specific circumstances, against imports from nations such as Japan with an overall trade surplus with the United States. The legislation, which Gephardt says does not deserve to be labeled "protectionist," is highly popular with many of the industrial unions.

In agriculture, which had never been a major area of interest to Gephardt, he has become the House cosponsor of a "supply management" bill drafted by Sen. Tom Harkin (D-Iowa), which is backed by the American Agriculture Movement and other farm groups active in the Iowa Democratic Party and strongly opposed by the American Farm Bureau Federation and other conservative groups.

On the issue of defense and disarmament, Gephardt gave a speech in Des Moines last month to a group of Democratic peace activists called STARPAC (Stop the Arms Race Political Action Committee). In that speech, Gephardt said "we didn't need to spend more money" on defense in the 1980s. He pledged to stop aid to the Nicaraguan contras "on the day I take office as president," to "halt our own nuclear tests at one kiloton, and challenge the Soviets to live up to their promise to join us," to negotiate "a mutual, verifiable ban on the flight tests of ballistic missiles," to "cancel any ongoing plans for 'Star Wars' {Strategic Defense Initiative} deployment . . . {and} agree with the Soviets to ban all SDI testing for the next 10 years."

In addition, Gephardt renewed 1984 nominee Walter F. Mondale's proposal for annual summit meetings and suggested direct meetings between U.S. and Soviet military officials as well, along with new joint space ventures with the Soviets.

Although Gephardt has voted for many weapons systems and large military budgets in Congress, the text of his speech -- distributed to many reporters since it was delivered -- contains no indications of his alternative defense programs.

Asked in the interview here whether he had felt pressure to shift his views and rhetoric to the left, Gephardt said, "You certainly meet people that have a particular view . . . one-issue people." But in no instance, he said, had he taken a position to placate or enlist a constituency and indeed believed that "if you can't satisfy them on some particular issue, then you just have to give them up as a vote."

He said his trade position and advocacy of an oil-import fee, for example, had cost him support in Iowa and New Hampshire.

A somewhat different perspective came from others close to him in the past or today. Joanne Symons, one of many former campaign workers for Sen. Edward M. Kennedy (D-Mass.) who has joined former Kennedy aide Carrick in working for Gephardt, said, "The whole dynamic of the process is to force you to the left. The Iowa caucus voters are liberal Democrats. The New Hampshire activists are liberal."

In Iowa, said Symons, a senior consultant to the Gephardt campaign, caucus-goers regard "a moderate as white bread . . . and they want steak. So Dick has the trade thing and Harkin-Gephardt {his farm bill} as red-meat issues."

Al From, former executive director of the House Democratic Caucus and now staff director of the Democratic Leadership Council -- a group of moderate Democrats that picked Gephardt as its first chairman in 1985 -- takes a more critical view of the process. "When you get into the campaign as a long shot, as Dick did, the moderate option is not really an option. You have to find a route that gets you into the game, and that means courting groups that have the capacity to organize for you. The system almost demands it -- and that's the problem."

But Symons noted that "there is a constant awareness that things you say in Iowa can come back to haunt you in the South." Gephardt cited an issue that he sees as a two-edged sword: the nomination of Robert H. Bork to the Supreme Court, which he strongly opposes. "I went down to Little Rock {for the convention of state legislators from the southern states} and answered their questions on Bork and it didn't set well with some people," he said. The same comments, however, drew cheers two days later at the National Women's Political Caucus.

So far, Gephardt's strategists and his southern supporters think he has not crossed the line and made himself unacceptable to southern moderate and conservative Democrats. They believe he can compete effectively with Sen. Albert Gore Jr. (D-Tenn.) for what many are calling "the Sam Nunn vote."

Rep. Marvin Leath (D-Tex.) said, "I think Dick is philosophically pretty much in the center . . . . Obviously, he'll move to the left in Iowa because Iowa is the most liberal state in the union. But some of us in the South wanted to get with him {endorse him} early to keep the left from pushing him off the cliff . . . and making him unelectable."

Rep. Buddy MacKay (D-Fla.), another early supporter, said he found it "disturbing that he {Gephardt} is having to accommodate to the crazy dynamics of Iowa . . . . I've been telling his advisers, 'Don't get so sensitive to Iowa you forget about the South.' A person has to be closer to Sam Nunn than to Iowa to be credible in the South."

"We know we have to craft a national message," campaign manager Carrick said. "The only trouble is, you spend so much time in Iowa, there's an instinct to say, 'Let's win Iowa and worry about the rest later.' "