The Bullets face a pivotal game today, not only in their quest for the NBA Eastern Conference championship but in their attempt to gain a base of fan support for future years.

Not since Washington challenged Golden State for the NBA title in 1975 has local interest in the team been so intense. Still the club did not sell out today's 1:30 confrontation with the Philadelphia 76ers at Capital Centre until yesterday afternoon.

"This is a big series for this franchise," said Coach Dick Motta. "We've got to get the fans back. If we can beat Philly, I think that will do the trick."

Many of those fans left after the Bullets lost to the Warriors four straight in the title series. Playoff attendance has not been good since, which is one reason the Bullets decided not to lift the area blackout on this game for television.

"Abe Pollin decided it wouldn't be fair to our paying customers to lift the blackout," a team spokesman said. "As soon as it was announced that Friday night's home game was going to be on TV, ticket sales for today's game fell off. It wasn't a good sign." insert after third graph:

Financier Louis E. Wolfson's Affirmed, with 18-year-old Steve Cauthen up for his first Derby ride, won the 104th "Run for the Roses" yesterday, holding off his arch-rival of a year ago, Calumet Farm's Alydar, by 1 1/2 lengths in a stirring stretch run. Affirmed's time was 2:01-1/5 for the 1 1/4-mile gallop on a fast, sunbaked track.

Affirmed, trained by Laz Barrera, captured $186,900 for his Harbor View Farm, plus the champion's traditional blanket of roses. He paid $5.60, $2.80, and $2.60. Alydar, trained by John Veitch and ridden by Jorge Velasquez, paid $2.60 to place and $2.40 to show, while Hickory Tree Stable's Believe It, Eddie Maple in the saddle, was third, another 1 1/4 lengths back, and paid $2.80 to show.

A crowd of more than 130,000 wag-trained by Woody Stephens and with ered a record $4,425,828 on the Derby.

The Bullets have sold out the last three playoff games and have had rising expectations before, only to be disappointed when the Bullets faltered in the playoffs. To avoid a repeat of that sequence of events, they feel they have to win today's game.

"The game is so, so important to us," said Motta. "Everything we've done so far will really be hurt if we lose it. Then we'd have to win a game in Philly to take the series, which would make our job tougher."

If the Bullets can win this fourth game, they would grab a 3-1 lead and need to take only one of the remaining three contests to advance to the NBA final.

They will probably have to play again without the services of center Wes Unseld.

Unseld. Who sprained an ankle late in the first game, has missed the last injury was still sore and that he couldn't put much weight on the foot. But he wouldn't rule himself out of today's contest and no one associated with the club would be surprised if he showed up in the starting lineup. tr for add two

"If Wes can play, he will start," said Motta. "I'm not going to let him sit on the bench and have the ankle tighten up." If Unseld is unable to play, Mitch Kupchak will be the starting center.

The Bullets won without Unseld in game three Friday night by hustling, shooting well, playing good defense in spurts and controlling the tempo. And the 76ers helped with a disjointed effort that was so bad Coach Billy Cunninghamlabeled it "a complete breakdown."