Members of the District's small Republican Party, faced with their first divisive primary, will have to choose Tuesday between ideology and pragmatism when they select a nominee for the City Council's at-large seat.

Pragmatists, along with most party leaders, have lined up, however reluctantly, behind 11-year Council member Jerry A. Moore, the only Republican on the 13-member body. Moore, a black Baptist minister, usually votes with the council's Democratic majority, but Republicans grudgingly concede that his broad appeal to blacks and Democrats will make him a certain winner in the November general elections.

Ideologically, however, many Republicans say privately they prefer one of Moore's two challengers, Joe Grano or Clinton B. D. Brown, both lawyers. Grano has toed the traditional conservative Republican line, and his vigorous campaign has excited many Republicans who were tired of Moore's Democratic leanings.

But Moore, 63, and his supporters have successfully spread the word, that in a city overwhelmingly Democratic (and overwhelmingly black), neither Grano, 35, nor Brown, 66, can win in November. In essence, Moore's message is: You may not like me, but I'm all you've got.

"It's a dilemma for me," said Ann Kelsey Marshall, a freelance writer who is running unopposed in the Ward 2 Republican primary. "It's a problem for a lot of Republicans. We cannot afford to lose a Republican seat on the Council, but on the other hand, you have Grano espousing true Republican ideology."

The conflict between Moore's claims of electability and Grano's ideological purity has split the small Republican party and provided the first lively feud old-time District Republicans remember in decades. Brown's underfunded campaign and his vigorous, middle-of-the-road attacks on both Moore and Grano has made the primary as colorful as any of the Democratic races. It's been complete with poster wars, public stumping, and even a ten-car motorcade through Washington.

The Moore-Grano feud came close to a finale with some last-minute politicking yesterday afternoon at a GOP gathering to promote, of all things, party unity behind the national ticket.

Moore had staged a grand entrance to the Republican party meeting, arriving in a motorcade and wearing his red-and-white Re-Elect Jerry Moore T-Shirt. But when the Moore ten-car caravan pulled up, Grano was already there, and had blanketed the meeting room, and the lamp posts outside, with his posters. Moore quickly dispatched an aide to put up posters of his own.

Moore, who changed from his T-shirt to a more conservative dark blue suit, told the Republicans, "We're going to win this race, this Bush-Reagan ticket, and I'm going to win too."

But Grano, introduced later, won a more enthusiastic burst of applause when he said: "I hope to represent you on the City Council and, more importantly, I hope to represent Republican thinking on the City Council."

Brown, who did not attend the meeting, said later in a statement, "The (Republican) committee made premature commitments to support Jerry Moore, before it even knew there would be two Republican challengers. It preferred Jerry Moore as a safe candidate" and expected the Republican voters to "blindly follow the leadership, right or wrong."

The local Republican party's executive committee endorsed Moore early last month, but from the reception Grano received -- and from the comments of Republicans afterwards -- it seemed clear that the Moore endorsement was less than unanimous with the Republican rank and file.

"We never had a vote on that endorsement," said one party member grudgingly. "If we had, I'm not sure it would have gone (for Moore)."

Moore is campaigning by stressing the fact that he was officially endorsed by the local Republican party. His newspaper advertisements carry a list of 60 names of supporters, mostly members of the local party committee.

But Grano said he is hoping that enough of the party members including some who only reluctantly joined Moore's list, like Ann Marshall -- will break rank and vote for his on Tuesday, on ideological grounds.

"Republicans are not an easy group to lead," said one Moore partisan, admitting that the party endorsement may be shallow. "They're very individualistic."

"Joe Grano has split up this party," said another party member. "Here is a guy who's not afraid to be a Republican. Jerry Moore only comes back to us when he's running for reelection."