In early jockeying for the 1988 GOP presidential nomination, some of the toughest fights are emerging in neighborhoods where Republicans are almost alien creatures: Detroit's black precincts.

The decision by Michigan Republicans to try to turn the Aug. 5 primary into the first test for prospective presidential candidates -- 15 months before Iowa's caucuses -- is forcing GOP strategists to work as hard in precincts where President Reagan lost by ratios as great as 40 to 1 as they work in those where he won.

Complex procedures requiring prospective presidential candidates to field thousands of candidates for precinct delegate also have forced these strategists to conduct grass-roots organizing where their party has literally no presence.

"It's tough to find people to run for Republican precinct delegate in areas like Detroit," said Ken Connolly, chief of Michigan operations for Vice President Bush's political action committee, the Fund for America's Future.

Keith Butler, black pastor of the Word of Faith Christian Center in north Detroit and an adamant supporter of Rep. Jack Kemp (R-N.Y.), said, "I think we're going to win. I think we've got it sewn up in the 1st and 13th Districts," the two black congressional districts in Detroit. "There isn't much of a Bush presence here," he said.

Bush forces have gained the backing of much of the black establishment in the Republican Party, whose goal is to line up as many pro-Bush precinct delegate candidates as possible.

"I'm working on it," said Dovie Pickett, chairman of the 13th District GOP and a Bush supporter, referring to a goal of persuading one person in each of 328 precincts of the 13th District to have 15 to 20 neighbors sign a petition, have it notarized and file it by 4 p.m. May 27.

The wild card in the contest is the Rev. Marion G. (Pat) Robertson, conservative evangelical television talk-show host and head of the Christian Broadcast Network. Robertson's appeal is far stronger to white fundamentalists than to blacks, and his rally last week in downtown Cobo Hall attracted about 200 to 300 blacks in a crowd of 3,500.

Andrea Harris, a black field worker in the 1st and 13th Districts for the Freedom Council, an organization closely tied to Robertson, acknowledged that "Detroit is primarily a Democratic community" but said, "Pat Robertson has the charisma for both parties."

For Kemp, victory in the 1st and 13th would help support his claim that he is best equipped to draw blue-collar blacks and whites to the GOP.

For Bush, these precincts could determine whether he maintains front-runner status and repeats his 1980 performance, when he defeated Reagan in Michigan.

For Robertson, who appears strongest in more rural western Michigan, winning at least a substantial minority of black precinct delegates would add needed legitimacy.

By law, each candidate must file a petition with names of 15 to 20 registered voters living in the precinct. In many black Detroit precincts, Reagan did not even get 15, an indication of how averse many blacks are to voting Republican.

In the politics of the Michigan primary, however, the near vacuum of black GOP support is irrelevent to the contestants.

Despite leaning overwhelmingly toward the Democratic Party, the 1st and 13th Districts will have three seats each at the Republican presidential convention, just like the state's 16 other congressional districts.

More important, the Michigan primary will be the presidential candidates' first test of strength, preceding for the first time the highly publicized Iowa caucus and New Hampshire's primary.

Precinct delegate winners in August will meet in January 1988 to begin selecting members of the Michigan presidential delegation.

Precinct delegate candidates are not identified on the ballot as supporting a presidential campaign, but Robertson, Kemp and Bush are seeking firm 1988 support by having their backers run for the posts. An expected 10,000 openings for precinct delegate are expected statewide.