By the time the District of Columbia's sexual assault bill reached the floor of the House earlier this month, the city already had forfeited the contest. Mayor Marion Barry didn't try to buttonhole any members of Congress, and his chief lobbyist made only a handful of phone calls to explain the measure.

In the internal politics of the House, meanwhile, the issue came to be viewed in distinctly partisan terms. House Speaker Thomas P.(Tip) O'Neill and other Democratic leaders, who generally go to bat for the District, became convinced that the Republicans were trying to trap them into an embarrassing vote in favor of sexual perversion.

The debate placed the city's delegate, Walter E. Fauntroy, in a difficult position. As a Baptist minister, he was uncomfortable with some of the bill's provisions, but as the city's voice on Capitol Hill, he felt compelled to fight for the measure.

And the outcome underscored the growing influence of a number of single-issue lobbies -- from the Moral Majority to the anti-abortion forces to the proponents of tuition tax credits -- that have begun to use Washington as a testing ground to win national attention for their causes.

"These special interest groups are looking at the District as a test tube," said Rep. Stewart B. McKinney of Connecticut, the ranking Republican on the House District Committee and a frequent ally of the city. "They can journey into a laboratory and say they stopped the gays. They couldn't do this on a national level, but they need victories to sustain their fund-raising and they get a lot of publicity."

The battle over the sexual assault law tells a great deal about the limits of the District's 6-year-old home rule government.

The Rev. Jerry Falwell and the Moral Majority essentially had free rein to conduct a nationwide crusade against what they termed sexual immorality in the nation's capital. And many city officials seemed resigned to the fact that when it comes to an important or emotional local issue, the Congress can pretty much do as it pleases.

"The city doesn't have the resources to muster that kind of campaign," Barry said after the vote. "Anyone who expects us to mount the constant pressure the Moral Majority can mount is either unrealistic or crazy."

It was more than two years ago when City Council member David A. Clarke (D-Ward 1) began drafting a bill to revise the city's criminal code, including many archaic statutes that were rarely enforced.

The new bill followed a nationwide pattern, broadening the definition of rape and repealing the criminal penalties for adultery, fornication, sex with animals and sodomy between consenting adults. It was considered a major victory for many women's groups and the city's increasingly influential gay community.

Some of Washington's clergymen were outraged that the council would condone such behavior. The Rev. Cleveland Sparrow, who heads the D.C. chapter of the Moral Majority, said he and his followers began to protest in June after published reports focused on a provision that effectively would have lowered the age of consent for sexual acts between children.

In July, the council agreed to delete that provision. But despite the protests of angry ministers who mobbed the District Building, the council passed the bill unanimously, and Mayor Barry signed it.

In any other city, the measure would have become law. But under the 1973 D.C. Home Rule Act, Barry was required to send the bill up to Capitol Hill, where a majority of either the House or Senate could overturn it within 30 congressional working days. Congress had used that power once before, on a 1979 measure restricting the location of chanceries, but never on a purely local matter.

In early September, two local church groups, The Baptist Ministers Conference of Washington, D.C. and the Committee of 100 Ministers, tried to win on the Hill what they had lost in the City Council. They complained to Rep. Philip Crane (R-Ill.), who knew little about the sex bill at the time. Crane quickly introduced a resolution to disapprove it.

"I don't think anyone feels comfortable trying to legislate morality," Crane said. "Amongst consenting adults, what's done in the privacy of one's home is basically one's business.

"But there were a few obnoxious features in what was overwhelmingly a good piece of legislation. As a former teacher, what struck me most was the provision on seducing youngsters which would have removed criminal penalties for teachers who have sex with consenting students 16 or older . There should be penalties to deal with that."

The Rev. John D. Bussey, pastor of the Bethesda Baptist Church in Northeast Washington and one of those who complained to Crane, said the ministers saw nothing wrong with taking their complaints to the Hill.

"We told Mr. Clarke even before it passed that we would go to the Hill," Bussey said. "Going to Congress is part of home rule, and we hope it stays that way."

The next attack came from Falwell, who made clear that his Moral Majority considered this a key vote and would campaign against any congressman who failed to see the light. "It would be a terrible thing if Washington, D.C. became the gay capital of the world," Falwell said.

The House District Committee, which is generally sympathetic to the city, was unimpressed. On Sept. 24, the panel voted down Crane's resolution 8 to 3. But Crane took advantage of a provision in the Home Rule Act that allows a single congressman to ignore the committee's vote by going directly to the floor with a resolution to veto a D.C. law.

As the Oct. 5 deadline for Congress to act drew nearer, however, there was little response from the city. Barbara C. Washington, director of the D.C. Office of Intergovernmental Relations, said that she and her 15-member staff were too overwhelmed by other duties to defend the sex law.

She did not venture up to the Hill during this crucial period, Washington said, because she also has to deal with the City Council and various federal and regional agencies, and she has only one full-time aide assigned to Congress.

"I don't have one-tenth of what I need to do the kind of job the city needs," said Washington, who formerly was minority counsel on the House District Committee. "Even if I stayed here every night and all weekend, I couldn't do all the work that needs to be done."

"I think our track record is exemplary, but we have to pick and choose our issues," she said. "No matter what we did on the sex bill, we questioned whether we could prevail."

To make matters worse, many of the newer, more conservative members of Congress knew little about the city, the concept of home rule or even the legislation at hand.

McKinney, for example, noting that few of his colleagues even know who Barry is, had recommended that the mayor hold receptions for 20 or so congressmen each week to talk about the city's problems. Until recently, however, the mayor has concentrated on a few key committee members and has made little effort to cultivate the new group.

One such member is Rep. David Daniel Marriott, a conservative Republican from Salt Lake City, who says he believes that adulterers should go to jail. Marriott acknowledged that he opposed the sex law without ever studying it. "I got the summary from my good friend Fauntleroy sic ," he said, in an apparent reference to D.C. Delegate Fauntroy.

Some of the District's longtime friends also had become increasingly cautious about coming to the city's rescue. McKinney said he still hasn't forgotten the Friday afternoon last spring when he told Barry over lunch that he was worried about signs that several city agencies were overspending their budgets. Barry calmly reassured him that there would be no deficit.

Four days later, McKinney saw a front-page headline announcing that the city was facing a possible $60-million deficit. "I nearly had a stroke," he said. Barry later blamed members of the City Council for leaking the news, but the damage had been done.

Others, meanwhile, either had lost patience with the District or felt that Barry had gone out of his way to antagonize them. When the House D.C. Appropriations Subcommittee directed the mayor to hire 200 more police officers earlier this year, for example, Barry ignored the order for months.

"Every one of us has had staff members who have been mugged, robbed and raped, and people up here are upset about these things," said Rep. John Porter (R-Ill.) "They didn't hire the officers and that created a lot of ill will."

In the past, the city usually has been able to count on solid support from Democratic leaders on the Hill. This time, however, the leadership was convinced that the furor surrounding the vote was being stirred up by the Republican right. Top Democrats such as Majority Leader James C. Wright of Texas and Ways and Means Committee Chairman Daniel Rostenkowski of Illinois refused to stand up for the city.

"It had nothing to do with D.C.," said Chris Mathews, a spokesman for O'Neill. "The whole purpose of the vote was to embarrass Democrats so the Republicans would have something to run against with the crazies. It would take you 10 minutes to explain that you voted for home rule, and it'd take them 30 seconds to smear you with that vote.

"We weren't gonna be set up like that. Unfortunately, the principle of home rule gets damaged in the bargain."

The speaker's office was tipped off when an aide to Republican Leader Robert Michel of Illinois asked whether the Democrats would try to delay Crane's motion beyond the Oct. 5 deadline. O'Neill's office replied that he would not block the vote.

Crane then sent a personal note about the sex bill to 234 selected members, along with a critical statement from Rep. Romano Mazzoli (D-Ky.), who is generally regarded as a supporter of home rule.

If the bill became law, Mazzoli said, "incest -- the most abominable outrage and crime against humanity -- will be decriminalized and considered appropriate conduct in the District of Columbia." He said the measure also "would give teachers a sexual hunting license."

As the final deadline approached, Crane's office sent an emissary to visit Fauntroy. The aide told Fauntroy that Crane would be willing to withdraw his motion if Fauntroy would announce that he had some problems with the bill and wanted the City Council to reconsider it. That way, Fauntroy was told, he could save face and avoid having hundreds of members of Congress vote against the measure.

It was a difficult moment for Fauntroy. He had told Mayor Barry that as a minister, he personally disagreed with some of the bill's provisions, but felt compelled to fight for the measure as a home rule issue. Fauntroy rejected the Crane offer.

"There was a lot of distortion and demogoguery in that debate," Fauntroy said later. "Given the limited time frame, I don't think we could have done much more. But all of us have to be more careful about not feeding legislation to these New Right groups that enables them to score points on us."

Fauntroy printed up his own fact sheet to explain and defend the legislation, but it was too carefully worded to have much impact. As a non-voting delegate, moreover, Fauntroy could not garner votes from his colleagues by promising his support on other issues. In addition, some members said his heart just wasn't in it.

On the morning of Thursday, Oct. 1, the House began a five-hour debate on the sexual assault law. The city had never distributed copies of the law for the members to read, but as the speeches droned on, Crane began handing out his own mimeographed summary:

"The D.C. act legalizes homosexual conduct, decriminalizes the seduction of children, decreases the penalty for forcible rape . . . This does not disrupt home rule."

As they filed in for the roll call vote, most members had little trouble making up their minds.

Thomas Foley, a Democrat from Spokane, Wash., said his gut feeling was that he could not trust the City Council.

Ron Marlenee, a Republican from Montana, said two of his friends were recently killed here and he wanted to send the District a message on crime.

For Robert McClory, a moderate Republican from Lake Bluff, Ill., it was his disappointment in the D.C. government. "I had been a staunch supporter of home rule," McClory said. "But I've just been terribly disappointed in the results I've seen, in the school system, in the bad publicity about Barry, in the poor handling of federal funds. My son taught English in the schools here and had to quit because the discipline was so bad."

McClory had another reason for voting against the bill: "It played into the hands of the gay activists, who I just deplore. I think they're sick people who need to be healed."

Charles Wilson, a Democrat from Lufkin, Tex., said he had no desire to risk his political neck when he realized the vote would be so lopsided. "It was a cheap vote," he said. "Why should I give the Moral Majority another issue -- so they can have kids running around with signs saying I support homosexuality?"

For Paul Simon, a Democrat from Carbondale, Ill., it was a sturuggle between his conscience and the dozens of letters and calls he received from his rural district. "It was a terrible thing," he said of the vote. "But you can't sell that kind of thing in southern Illinois. I'm in Bible Belt country."

And for one veteran liberal Democrat, it boiled down to this question: "How would you like to spend your goddamn campaign trying to explain how you're not in favor of people having sexual relations with animals?"

The final vote was 281-119. McKinney looked at the tally sheet a few days later and said: "It never had a prayer."