A group of politically prominent Washingtonians and a retired Long Island jeweler who are seeking to open a jai alai arena here are almost single-handedly financing the final days of the campaign to legalize gambling in the District of Columbia.

In the last few days, shareholders in Washington Jai Alai, Inc., have pumped $27,000 into the treasury of the umbrella group that advocates approval of the May 6 referendum on legalized gambling.

The money includes $4,000 to pay for mailing 25,000 brochures to voters, $11,000 to purchase a list of registered voters and their telephone numbers and $12,000 to pay gambling campaign staff workers for the last three weeks.

With Washington Jai Alai's latest transfusion of cash into the pro-gambling campaign, it now has financed nearly half -- $34,000 out of $70,000 -- of the effort to first get gambling referendum on the May 6 ballot, and then to promote its passage. Gambling opponents have raised only $11,000 so far.

Brant Coopersmith, chairman of the D.C. Committee on Legalized Gambling, said Washington Jai Alai's large donation to the campaign does not undermine what he and other gambling supporters feel is a broad base of support for gambling.

"I'm grateful for Washington Jai Alai or anyone else who wants to support this initiative," said Coopersmith, the Washington-area director of the American Jewish Committee. "But that doesn't mean that Washington Jai Alai dictated the (contents of) the referendum. They didn't have anything to do with the (D.C. Gambling Study) Commission report," which recommended the legalization of gambling here.

But the Rev. John D. Bussey, a Baptist minister and chairman of two antigambling groups fighting passage of the referendum, said that the large donation from Washington Jai Alai amounts to "an unfair financial advantage and makes us wonder whether these people are concerned about making money or giving the people something they want."

Washington Jai Alai is one of at least three firms seeking to operate jai alai, a fast-paced Spanish sport played on a three-walled indoor court, in Washington.

Gambling opponents have been focusing their efforts to have the all-or-nothing proposal rejected on jai alai, which has been the subject of major game-fixing investigations in two of the four states where it is now played.

The referendum, if approved by District voters, would legalize parimutuel betting on jai alai and dog racing, daily numbers and lottery games, bingo, raffles and social betting where the organizer reaps no profit.

Justin J. Schick, a retired Long Island, N.y., jeweler living in Florida, owns 45 percent of the Washington Jai Alai and the rest of the stock is split among Washington residents, with none of them having more than 5 percent each.

Included among the D.C. residents who have invested in Washington Jai Alai are former D.C. Corporation Counsel Charles T. Duncan; developer Theodore Hagans, realtor Flaxie M. Pinkett, funeral home owner Robert Grayson McGuire, Delano E. Lewis, an assistant vice president of the C&P Telephone co.; Tyler Abell, a Washington attorney and husband of Bess Abell, executive secretary to Joan Mondale; Washington attorney Richard K. Lyon and Martin E. Firestone. Lyon and Firestone have performed legal work for the company to account for their 5 percent equity.

Firestone, a lawyer for Washington Jai Alai and one of the chief drafters of the 43-page gambling law on which D.C. residents will be voting, said that "no one at Washington Jai Alai is particularly happy at having to (make the large contributions) when it's only going to give them a shot (along with other companies) at running jai alai," if the referendum passes.

But Firestone, a Washington attorney, said that Washington Jai Alai donations were necessary, because "without it, the campaign probably would have come down to a crawl or a screeching halt. It was anticipated that others would come forward (with donations), but nobody has."

He said the money has been raised by asking each of Washington Jai Alai's investors to make donations based on their percentage ownership of the company.

The pro-gambling effort has also received other large donations from contributors with a special interest in seeing legalized gambling approved here.

Four out-or city firms that manufacture computers to run lotteries and print lottery tickets have donated a total of $19,000 to the campaign, including $12,00 from General Instrument Corp. of New York City and $6,000 from Scientific Games Development Corp. of Atlanta.

"We want an equal chance to bid" for a city lottery ticket contract, said James F. Trucks, corporate counsel for Scientific Games, which prints lottery tickets. "We are quite frankly interested in seeing new lotteries. There are only 14 now and we'd like to see a 15th. It's the only way we can build our business."

In addition, D.C. liquor dealers, who would like to operate lottery ticket outlets in their stores like their competitors in Maryland, have contributed about $5,000 to the pro-gambling campaign.

Seven individual gambling supporters, including Firestone, Coopersmith and Lyon, have made $1,000 loans to the campaign, a small portion of which has been repaid to them.