Central America's civil wars have reached the drawing rooms of Washington, dividing the capital's liberal Democratic establishment into two anguished camps and sapping liberal opposition to President Reagan's aid to the Nicaraguan rebels.

A handful of liberal activists has broken ranks to support U.S. aid to the rebels fighting Nicaragua's leftist regime, declaring that some of the contras, as the rebels are known, are fighting for democracy and deserve American support.

The majority of liberals disagree. But the apostasy of the dissidents has shown a serious fraying of the Democrats' once-solid front against the Reagan administration's policies in Central America. To some, it reflects a basic rift between activists fighting to preserve the noninterventionist policies of the Jimmy Carter years and a small contingent of others, mostly elected officials, who want to move the Democrats closer to the Reagan era's center.

The debate has aroused unusual passion, pitting old comrades from the Vietnam antiwar movement against each other. At the think tanks, congressional offices and dining room tables where Democratic policy is made, there have been charges of betrayal and McCarthyism. Jobs have been lost; friendships ruptured.

"I don't get invited to weddings anymore," said Central America scholar Robert Leiken, one of the new apostates. "Some people on the left, from my days in the antiwar movement, have never forgiven me."

The conflict also appears to have drained liberal enthusiasm for the coming debate over U.S. assistance to the contras, which is $27 million in nonlethal, humanitarian aid that expires in March. The issue is expected to come up for another vote in Congress early this year. Until recently, most liberals were confident that the Democratic-led House could block a new aid request or at least maintain the current prohibition against U.S. military help for the contras. Now they are not so certain.

"I don't think there is a consensus on Central America," said Rep. Stephen J. Solarz (D-N.Y.), a member of the House Foreign Affairs Committee. "I think it's up for grabs."

"The opposition is leaderless," complained Rep. Robert G. Torricelli (D-N.J.), another liberal on the panel. "Support for the administration's position has been slowly building."

Solarz and Torricelli said that they will fight renewed aid to the contras, but both are pessimistic about their chances of success.

"The question isn't whether the administration can get the current level of assistance -- that's certain," Torricelli said. "The question is whether they can get lethal aid. I think they probably have the votes where they can."

Until recently, the Democrats considered Central America one of their best issues: an area where President Reagan's policies were clearly unpopular.

House liberals slashed Reagan's requests for aid to rightist-dominated regimes in El Salvador, put tough human-rights conditions on what aid they did approve and blocked aid to the contras for more than a year.

Coincidentally, it was the liberals' success in forcing reforms in El Salvador that opened the first rift in their ranks. When death squad murders declined and moderate Jose Napoleon Duarte was elected president, most congressional Democrats switched to supporting increased aid for El Salvador. But leftist-oriented human-rights activists continued to protest the aid, charging that Duarte's regime had not reformed enough to deserve U.S. help.

"El Salvador was really where the break in the consensus came. It was the path to all our apostasies," said Bruce Cameron, a human-rights lobbyist who supported the Duarte regime and later lost his job over the contra issue.

The second watershed issue was the behavior of Nicaragua's Sandinista government, which came to be viewed by increasing numbers of liberals as unnecessarily repressive, even in the face of the U.S.-sponsored contra war. Sandinista youths physically attacked opposition activists during the 1984 presidential election campaign, and some Sandinista leaders dismissed the vote as a meaningless formality. After the election, the regime cracked down on dissidents and moved increasingly closer to the Soviet Union.

The changes dismayed liberals, many of whom had championed the Sandinistas in earlier years. Some grass-roots activists still defend the government, but in Congress nearly all Democrats now take pains to say that their opposition to the contras does not mean they support the Managua regime.

The result has been a three-way split. In one camp are the activists who oppose aid to the contras under any circumstances as immoral. "The contras and human rights are incompatible, period," said Ann Lewis, national director of the liberal Americans for Democratic Action.

In another are those few, including Cameron and Leiken, who have "defected" to the administration's side in supporting aid to the contras even though they insist that their goal is to bring about negotiations toward a compromise between the Sandinistas and the rebels. They also criticize the administration for failing to negotiate.

And, in the middle are an unknown number of Democratic congressmen who say they oppose aid to the contras today but might be swayed if they could be convinced that Cameron and Leiken are right.

"There is a group that believes that some aid to the contras could be justifiable under some circumstances as a way of giving support to a political effort," said Rep. Matthew F. McHugh (D-N.Y.). "The key is negotiations. If the president could demonstrate that he's serious about negotiations, if he would appoint a negotiator who has credibility . . . that would go a long way toward convincing me."

Viewed another way, the conflict is between activists who talk in terms of moral absolutes and politicians who more often criticize the administration's policy because it doesn't "work," and who are looking, without much evident success, for an alternative policy that would clearly work better.

"None of the liberals outside Congress have asked me what I think," Cameron said. "But congressmen have."

Until last spring, Cameron was chief human-rights lobbyist for the ADA, universally acknowledged as one of the liberals' most effective congressional engineers.

Then he began expressing doubts about the ADA's absolute opposition to aiding moderate elements among the contras. He went on leave from his job and helped Rep. Dave McCurdy (D-Okla.) put together a compromise package that committed Reagan to negotiate with the Sandinistas in exchange for nonmilitary aid for the rebels.

The compromise helped win what the administration calls "humanitarian" aid for the rebel army (although Reagan aides later said that the president did not consider himself bound to negotiate). It also cost Cameron not only his ADA job but also seats on the boards of two human-rights organizations that he had helped found.

"I thought the human-rights language was good, that we could test the administration with it," Cameron said. "It turned out that the liberal critique is absolute . . . that there was a purity test and I failed it."

Lewis, who told Cameron that he could not return to the ADA, replied: "Our policy is simply that we disapprove of any aid to the contra forces. He may describe it as a very small step; I can't see that. It may be very small in distance, but it's very significant."

Cameron, a Vietnam antiwar activist who once organized campus teach-ins in praise of the Viet Cong and helped win U.S. aid for the Sandinista regime when it took over in 1979, is now trying to assemble a bipartisan support group for his middle-of-the-road policy. He said that he still considers himself a human-rights lobbyist despite what he refers to as "my pact with the devil." And he accuses his former colleagues of maintaining a "double standard" that lets them concentrate their fire on rightist regimes while sparing the left.

He is not alone in his anger at the activists. John McAward, a former human-rights lobbyist for the Unitarian Universalist Service Committee, resigned after he was accused of supporting the administration view on El Salvador too often and of getting bogged down in the politics of legislative compromise. "The people who know the most about the region are sometimes six months ahead of the rest of the country," he said.

Leiken, a scholar at the Carnegie Endowment for International Peace, said: "The issue is very important to the world view of many liberals . . . . They're painting it in stark and moralistic terms. It's very difficult for most liberals in Washington to move away from their fixed positions. There are so many vested interests involved: fellowships, positions, organizations."

But there are also subtle signs of a possible thaw in the liberal debate. Last year, Leiken published an article harshly critical of the Sandinistas in The New Republic, the theoretical journal of rightward-moving liberals. This year, he was published in The New York Review of Books, the guiding light of 1970s liberalism.

"That's significant," said one of the liberal dissidents. "A lot of people didn't want to see Leiken's article printed . . . . The debate is still in its infancy, but it's opening up.