The get-out-the-vote rally held at the Ebenezer A.M.E. Church in Fort Washington Oct. 28 attracted a small, quiet crowd of about 60. Wintley Phipps, the gospel singer who introduced Jesse L. Jackson at the Democratic National Convention, sang, and two county judges who are campaigning to retain their seats shared the small pulpit.

The scene was a far cry from a similar rally at Ebenezer last spring, when more than 500 people squeezed into the church and spilled out onto the sidewalk in order to greet then-candidate Jackson during one of his two high-energy Maryland visits.

Louis Shockley, the pastor of Gethsemane Baptist Church in District Heights, publicly despaired at the size of the Oct. 28 crowd.

"There are empty seats in the house," he said from the pulpit. "And that's why things are the way they are. Unless you have the big muscle -- and Jesse is the big muscle -- nobody shows up."

Jackson's presence as the only black candidate in the Democratic presidential primaries has been creditedwith attracting record numbers of black Prince George's County residents to register and vote in the May primary election.

Organizers said that they did not adequately publicize the recent rally and that they would have expected a larger crowd had they been able to get Jackson to attend.

"I don't sense a groundswell of enthusiasm for Walter Mondale in our congregation," said Grainger Browning, Ebenezer's pastor. "Besides Jesus, Jesse Jackson was the most popular person in our church."

But, he added, he expects his congregation to vote Democratic.

The Jackson victory six months ago has spawned a series of minor power struggles within the county's Democratic Party. But the fate of the county's black vote in the general election has become a rallying point for party strategists, who view the county as the wild card in the struggle to win Maryland for Mondale. Blacks make up 37 percent of the county's population, according to the 1980 census. ELECTION '84 ENTHUSIASM OF PRIMARIES WANES

Prince George's County and Baltimore, because they are populous, traditionally Democratic strongholds, are considered to be key to a Democratic victory in Maryland on Tuesday. When Maryland was one of only six states that President Carter carried in 1980, he won by only 46,000 votes -- largely because of pluralities of 120,000 votes in Baltimore and 20,000 votes in Prince George's.

Prince George's elections administrator Robert J. Antonetti said that even though 43,401 new voters have registered since the primary, he has noticed that there has not been the same organized push to bring in new black voters as there was before the primary.

"Everyone else seems to be convinced now of what we knew all along, that the black vote was going to be the deciding factor in Prince George's," said Steven Tillett, a program associate with the National Coalition on Black Voter Participation.

Democratic Party officials are hoping to duplicate or better the 43 percent primary voter turnout in the county, which was boosted in large part by newly registered voters supporting Jackson.

Attention has focused on Jackson's "rainbow coalition" supporters, who earlier this year were openly unhappy with the Mondale campaign, an attitude that mirrored Jackson's national stance. Although Mondale and Jackson have patched up their disagreements and both sides say they are working to defeat President Reagan, the local alliance remains uneasy.

Both mainstream white and newly empowered black rainbow coalition Democrats say that such conflicts have arisen because both sides are working to establish independent footholds from which to launch their 1986 election campaigns.

"We're looking at 1986 as the first real test of our strength without Jesse," said one black politician who asked not to be identified.

The latest skirmish between the two camps surfaced when Jackson supporters complained that sample ballots sent to black Democrats by the county party carried a posed photograph of U.S. Rep. Steny Hoyer (D-Md.) standing next to Jackson. Hoyer, a Mondale delegate to the San Francisco convention, is considered a likely 1986 target for the coalition.

The rest of the sample ballots carried the traditional Mondale-Ferraro message but no photograph of Jackson. The local Jackson supporters say they are suspicious that politicians who would not support Jackson in the primaries are attempting to capitalize on his popularity in the black community.

"We certainly don't like it," said Alvin Thornton, who is active in the local rainbow coalition. "It's clearly going a little too far."

State Del. Gary Alexander, who is head of the county Democratic Party, conceded that the Jackson-Hoyer picture on the sample ballot was meant to be a "motivational force" aimed at turning out the black vote.

Publicly, party officials are voicing great expectations about black voter turnout in the county. "I think the turnout is going to be greater than it was in 1980 for Carter," said Michael Frazier, the Maryland-Delaware field director for the Democratic presidential ticket. "They're going to get Mondale's vote out in Prince George's County."

And rainbow coalition leaders, who declared that the primary victory signified the beginning of a new era in Prince George's County politics, must prove that Jackson's win was no fluke.

"Just in chatting with people, they're beginning to understand the message now that Reagan is the enemy," said Bennie Thayer, the Kettering businessman who heads the state rainbow coalition and is a national vice chairman for the Mondale campaign.

Thayer and others acknowledge that the Jackson primary fervor is missing this time around in the black community, but they recognize that a depressed black voter turnout on Tuesday will undermine their future efforts.

"The issue is not whether or not our chosen candidate will win," Eldridge Spearman, an ordained minister who is a member of the county Democratic Central Committee, said at the Oct. 28 rally. "The issue is whether you will let your light shine in the ballot box."