David Abramson has a bomb to defuse. As the new advertising consultant for the Washington Federals his task may not be as difficult as the one faced by representatives for, say, the Edsel or clorophyll chewing gum, but he is not underestimating the difficulty of convincing people to lay down their garden hoes and parasols and head to RFK Stadium to watch a 1-10 football team struggle in the sun.

"They've got to stop losing," said Abramson, who was hired by the team last week. "The history of sports says that you can only have a New York Mets once in a long while. And that team was successful at the start because people laughed at them. But I don't think the Federals want to be laughed at."

Clearly, Abramson has missed some of the team's more hilarious moments. But he is right. The Federals' tragicomic attempts to defeat their rivals induce more yawns than giggles. And after a crowd of 38,010 attended the team's opening game, the crowds at RFK have been dwindling, fair weather or foul.

As a result, Abramson and the Federals management face two difficult tasks. At the very least, they must get this year's 19,000 season ticket holders back in the stands and they must try to get those same customers to renew their orders for next year. But when 11,369 season ticket holders decide to let their tickets go to waste as they did when the Federals played the Stallions on a sunny May 1, there is every indication that Abramson's best hopes are to regain early season success.

"For the rest of this year we've decided to concentrate on the theme of '100 percent effort,' " Abramson said. "We can't guarantee victories. We can't promise what we can't be sure of delivering."

Andy Bernhard, head of group ticket sales and son of owner Berl Bernhard, said, "All you can do is hope to pull it out. There's just so much people will accept."

Four home games remain on the schedule: Boston, New Jersey, Los Angeles and Philadelphia.

"We don't have that much advertising money left, so we decided to concentrate our efforts on two games, New Jersey and Los Angeles," Abramson said. "New Jersey because of Herschel Walker and Los Angeles because, well, that city has a magical appeal, and I think we can be competitive with that team."

As Team America's advertising consultant, Abramson arranged to have the Beach Boys play before the team's June 12 game against the Fort Lauderdale Strikers. No such large-scale promotions are planned for the Federals.

Bernhard said present season ticket holders will receive discount coupon books at renewal time. "It's just a little something to show we care," Bernhard said.

Clearly, other USFL teams, even those enjoying more commercial and athletic success than the Federals, are wary that this season's no-shows will be next season's no-buys.

Tad Taube owns the Oakland Invaders, a franchise considered the league's third most successful after Denver and Tampa Bay, respectively. Drawing on the Bay Area market, the Invaders sold 26,000 season tickets. When the Invaders played the Federals Monday night, the team announced that 25,900 tickets had been "distributed." A weekly press release issued by the USFL offices in New York read, "25,900 observed Oakland's Monday night conquest of Washington."

But that was not exactly true. One San Francisco sportswriter estimated the crowd at 16-17,000. The Invaders refused to announce the actual attendance.

Interviewed after the game, Taube said, "We never announce the actual attendance. That's our policy. The no-shows are meaningless. What counts is the number of tickets sold."

Don't chronic no-shows forecast problems for the following year?

"I don't think so at all," Taube said. "I think we'll get them all renewed."

Taube is far from relaxing in his pursuit of more ticket sales. At the Federals game, there were giveaways for everything from a new car to an all-expenses-paid trip to Africa.

Denver is another team that does not announce its no-show figures. "That's because Mile High Stadium just doesn't have any turnstiles," said George McFadden, a USFL spokesman.

Despite the mixed reception accorded the USFL so far, the league continues to project optimism about its future. A third 1984 expansion franchise officially went to Houston yesterday, to be owned by a group including agent Jerry Argovitz as general managing partner. Argovitz said his coaching candidates include three former NFL head coaches--Jack Pardee (Redskins, Bears), Marv Levy (Chiefs) and Leeman Bennett (Falcons)--and that he was negotiating for the Astrodome or Rice Stadium as home field.

"Expansion proves that these guys are in it for the long haul no matter what happens in the short term," Abramson said. "One thing that this league has that the World Football League didn't was heavy hitters in the financial department. They can afford to take some losses for a while if necessary."