Marion Barry, the proud and confident come-from-behind Democratic nominee for mayor, stood at the end of the Georgetown living room, near one of the two charcoal-gray maarble fireplaces that framed 15 shelves of 18th-century, salmon-and-white china plates.

He was in "Barry Country" - a precinct in which he outpolled Sterling Tucker, his closest Democratic opponent in an otherwise close primary election last month, by a margin of more than 2 to 1. And now Barry was authoritively imploring his wide-eyed supporters, who spilled over into the high-ceilinged Victorian hallway, to give him an even larger mandate in the Nov. 7 general elections.

"We ought to make sure that that candidate, whatever his name is, doesn't get many votes," Barry said of Arthur A. Fletcher, his Republican opponent in November. "We ought to set a goal of 80 percent. We don't want a landslide. We want an avalanche."

With only three full weeks remaining before the Nov. 7 election, Barry appears, on the surface, to be putting together the makings of such an avalanche, while the Fletcher campaigns, touted as the Republican Party's best chance to make a name for itself in this overwhelmingly Democratic city, has yet to get really rolling.

Fletcher, hoping to capitalize on strong anti-Barry sentiments among some voters and on the after effects of a close and sometimes bitter Democratic primary, has raised only $28,444 - one tenth as much money as Barry.

Fletcher does not have the money for a major media campaign to build name recognition. The thousands of dollars he was to receive from the national Republican war chest to draw more blacks into the party by putting up a good fight in this predominantly black city have gone elsewhere in the country, according to Fletcher.

He feels, a weary-looking Fletcher told one audience last week, like a businessman who was about to go out of business and all of a sudden there was a great demand for his product.

"When (Barry) won the primary, people from one end of the District to another, regardless of social or economic class, said, 'Yeah, there is another candidate'," Fletcher said. "The requests for appearances are coming so fast that I really can't cover them all. The interest has been fantastic."

But Fletcher appears to have few ward coordinators or precinct captains. He refuses to name those he says he has. His campaign workers, he said, are chipping in money to pay for posters. Many blacks are leery of him because of his Republican label. And Marion Barry is mostly ignoring him.

Barely,since the primary, have the two appeared at a candidate forum to debate, Fletcher frequently goes to the forums. But Barry, who religiously trekked the community forum circuit during the primary, is spending most of his time trying privately to heal wounds among fellow Democrat regulars.

Fletcher openly brags that a series of upcoming joint appearances on television could be decisive to the outcome of the election. But the first such appearance is still a week away.

The political calm that meanwhile settled over the city has covered up problems Barry still faces since narrowly defeating Council Chairman Tucker and Mayor Walter Washinton in last month's Democratic primary, in which Barry won 34 percent of the vote.

The Democratic Party was sharply divided among the three candidates, with each having a strongly loyal following. Nearly two-thirds of the city's Democrats voted against the eventual nominee. And, in a largely black city where many blacks jealously guard the political prominence they have gained during for short years of limited home rule, a significant protion of Barry's political base is made up of whites.

"People are very concerned," said one leading city Democrat privately, "that Marion does not represent the community. He represents the people who are trying to take over the community, whites and the upper class, the ultra liberals and the gays and The Washington Post" (whose editorial page vigorously endorsed Barry).

"To a lot of people it's no longer about party," said the Democrat, who supported one of Barry's opponents. "Now it's about race."

For several weeks, the Barry organization has been hoping to hold a unity press conference at which Barry, Tucker, Washington and Del. Walter E. Fauntroy (who supported Tucker) would formally join hands. So far the press conference has not come off. Barry campaign aides contended the problem is oneof "scheduling."

Barry has an enormous. "We're Coming Together" dance scheduled for this week at the Mazna Gallerie in Friendship Heights is far Northwest Washington. Nearly every imaginable top city Democrat is listed as a sponsor, including Tucker, Washington and Fauntroy, top officials of their campaigns, several congressmen and most Democratic members of the City Council.

Barry has also garnered the financial support of most of the city's leading businessmen and the endorsement of the organized labor leadership. He is expected to announce next week that many of the ministers who supported Tucker and Washington in September will now back his candidacy. All three constituencies have been integral parts of the city's Democratic party.

In order to bring more regular Democrats who supported other candidates into his camp, Barry also has been holding a seriesof "healing parties," such as that given last Sunday at the roomy, woodframe Chevy Chase home of Barbara and Tad Baldwin.Standing with Council member Poly Shackleton (D-Ward 3), who reluctantly endorsed Tucker near the end of the primary campaign, and with school board member Betty Anne Kane, the party's nominee fro an at-large seat on the council, Barry told the audience, "Polly and I have come to an agreement. We might temporarily separate, but we will never divide."

"My attitude is that the primary is over and the people have decided and the nominee is Marion Barry," he said. "I intend to be the mayor of everyone - the young the old, the white, the black, the Jew, the gentile and those that don't believe in anything. 'I'm for that, too.'"

When Fletcher announced his candidacy in late April, he said he would campaign heavily during the primary, even though he would have only token opposition and most attention would be focused on the Democratic contest.

But he said last week, his primary campaign drew little publicity from the news media, so he was able to raise only sparse campaign funds. As a result, with the general elections approaching, Fletcher is still scurrying to put together the major components of a campaign organization and at the same time gain widespread exposure.

Many of Fletcher's campaign appearances have been in Ward 3, where Republican constitute about one fourth of the voters - more than in any other city ward. But he is also, he said, concentrating efforts in wards 4 (upper Northwest Washington), 5 (most of Northeast Washington west of the Anacostia River) and 7 (far Northeast and Southeast).

Those three words were won by Walter Washington in the primary and Fletcher feels that is where that he is most likely to gain support from disgruntled more conservative Democrats. The three wards are also among the largest in the city with regularly high voter turnout.

Fletcher has already gained the support of the Rev. Andrew J. Allen, pastor of First Baptist Church of Deanwood and a strong supporter of Washington. Allen and the Rev. Jerry A. Moore Jr., the loose Republican on the City Council, have been helping to organize support for Fletcher among politically influential ministers and are expected of a clergy group supporting Fletcher's candidary.

Fletcher has no television or radio ads, claims the existence of a telephone book that he returns to show to the press, and says a large number of Democrats whom he will not name are supporting his campaign.

"I'm satisfied," Fletcher said last week, "that black Democrats in the District of Columbia have no hang-ups in voting for me. I'm gonna get a surprising number of crossovers.

"It could be enough to pull it off," he said. "Particularly if I get a break or two."