Estimates of Spectacular Bid's worth rise faster than the price of a six-pack of diet beer. The big horse began Derby Week insured for $14 million. Whenever Bud Delp speaks, that number grows. Today, it leveled off at $20 million. So, in the glorious morning here, assembled journalists took notes as a man fed a horse a doughnut. We half-expected Spectacular Bid to dunk it first.

"He's been wanting his doughnut," said Delp, 47, the survivor of hard times on bush tracks who trains the favorite in Saturday's Kentucky Derby. "He's pawing the ground, asking for it."

After his morning constitutional, which amounted to a leisurely two-mile gallop in the shadow of Churchill Downs' majestic twin spires, Spectacular Bid walked in Barn 41 for a half-hour or so.

The Derby often puts horse trainers to shaking. Perhaps furniture movers toting fine china have a more delicate task than a trainer bringing a horse up to the world's most famous race. But not by much, for 3-year-old thoroughbreds are notoriously fragile. The smallest misstep, the slightest nick of an ankle against the stall wall, can ruin months of planning.

A trainer once escaped inquiring reporters by hiding behind his horse in its stall. Occasionally, he would call out, "For God's sake, don't quote me." When Damascus failed as the heavy favorite to win the 1967 Derby, his trainer blamed it on the band that played "My Old Kentucky Home" during the post parade. "Too much brass," he said.

Bud Delp is having the time of his scuffling life. "This is show biz," he said the other day. It is his job, he said, to keep the reporters' pens scratching. So he told them he had asked Howard Cosell to bring an extra toupee that he could borrow. "I can't remember if Howard laughed," Delp said, laughing. And he recited a poem that went . . .

If Bid wins by two that'll do.

If he wins by five, we'll jive.

If he wins by nine, that'll be fine.

"I just made that up in the car on the way to the track," Delp said. "You can say I'm taking a page out of Muhammad Ali's book."

Pause.

Smile.

"But pretty soon Ali will be taking pages out of my book."

Anyway, Delp pulled a doughnut into three parts and stopped Spectacular Bid.

"He likes the glazed ones. The sugar. I don't give him one on race days. I just hold my hand out like I've got one. It calms him down."

As newsapermen will do, the literary masters dug deep into this revelation that a $20 million horse likes glazed doughnuts. Someone asked if Spectacular Bid took his doughnut with coffee.

"No stimulants," Delp said slyly. "After big races, though, I'll give him a chocolate doughnut."

In three chomps, Spectacular Bid devastated his morning goodie. Delp, who spent one day wired for sound for a piece to be used on a Walter Cronkite news show, then asked selected reporters - "Those fellows who didn't hear me earlier" - to join him in a tack room, where he turned down the show-biz volume a bit.

This is the horse trainer who has never won a Triple Crown race, never before had a horse in the Derby for that matter. This is the claiming-horse popoff, to use a local characterization, who said Spectacular Bid could beat Secretariat, Seattle Slew and Man o' War. "Only an act of God can beat Bid," Delp said.

In the tack room today, Delp admitted he could be wrong about that.

He is worrying about Flying Paster, the California colt who demolished his contemporaries there. Although many horsemen feel California colts are consistently overrated - the times are so good skeptics believe the Californians run downhill on concrete - Delp isn't counting on it.

"I'm afraid Flying Paster is a great horse," Delp said.

Someone asked the trainer to imagine a scenario in which his horse lost the Derby.

"I can't imagine it. The only way this horse can lose the Kentucky Debry is if Flying Paster is as good as Secretariat. I think Spectacular Bid is better than Secretariat. But I might be wrong there."

Speculators of doom see Ronnie Franklin, the 19-year-old jockey, as Spectacular Bid's fatal flaw. His ride in the Florida Derby was unanimously panned. Twice, he put the horse in a box, and only because the horse is a $20 million athlete could it overcome the rider's mistakes to win.

Delp said he could have murdered Franklin that day. He berated him obscenely and publicly. But the kid lives with Delp, almost as if he were an adopted son, and the next morning, the trainer said, "I put my arm around him and said I might have been too hard on him."

He still thought the ride was horrible, and he gave the owners, Mr. and Mrs. Harry Meyerhoff, a list of five riders to take Spectacular Bid to the Derby. The possibilities were Bill Shoemaker, Jacinto Vasquez, Chris McCarron, Darrell McHargue and Franklin.

When Meyerhoff chose Franklin, sentimentalists believed it a choice made from the heart as much as from the head.

"It may have been," said Delp, who insisted he had left it up to the owners. "But Bid's won eight in a row by a total of 60 lengths for Ronnie. You can't take anything away from the way the horse runs for him . . . If Ronnie continues with the desire he has now, he could be a great race rider. He's exactly the same kid he was when he was working for me for $80 a week. He's grateful to be on this horse. He's confident and he's relaxed."

Abruptly, Delp asked if anybody wanted a close look at his horse, "This horse is like a bank vault walking around in the open," he has said. But he took a passel of reporters up to the stall door and turned the horse sideways. He was proud.

"Does he look like he needs groceries?" Delp said. "He is dead ready, I just want the track to be as fast as it was the day Secretariat ran."

Secretariat set the Derby record of 1:59 2/5 in 1973. And what will Delp do if Spectacular Bid loses? How will the man behave after saying his noble steed could outrun Man o' War?

"I will probably look in a mirror and say, 'Delp, you're a dumb SOB," he said.