Forty-eight hours ago, Sunny's Halo was a national hero. Today he is a forgotten horse--a badly beaten sixth-place finisher behind Deputed Testamony in the Preakness.

His trainer, David Cross, could offer no major excuses for the defeat. The colt, he said, had come out of Saturday's race in sound physical shape. "His skin rash didn't affect his performance," Cross said. "It just wasn't his day. I tip my hat to the winner."

To casual fans, the fact that a horse can win one race and then lose under similar conditions by nearly a dozen lengths is a confirmation of the inscrutability of the game. But handicappers using the proper tools can examine the results of the Kentucky Derby and the Preakness and find them logically consistent. The two races, in fact, could be textbook examples to support the validity of modern trends in thoroughbred handicapping.

Over the past few years, increasing numbers of bettors have adopted the techniques known as "trip handicapping," which is not so much a system for picking winners as it is a new way of looking at races.

Traditionalists tend to accept the results of races at face value; they hail whoever crosses the finish line first. But the trip handicappers argue that the way a race develops will often determine its outcome. The fact that a horse won or lost, that he ran fast or slow, is almost irrelevant unless we examine how he did it.

Sunny's Halo won the Kentucky Derby after everything broke right for him. He saved ground on the turns; he avoided the heavy traffic in the 20-horse field; he set a comfortably slow pace so he was strong enough to withstand the challenges of the stretch-runners. Everybody was impressed by the ease and authority with which he had won. In fact, the race was so easy for him that it didn't prove much; Sunny's Halo hadn't shown that he could win under adverse or even neutral conditions.

In the Preakness, he got the chance to face adversity. He was bumped coming out of the gate, though the trouble should not have stopped a superior horse from winning. He had to race wide around the first turn. He had to chase Desert Wine as the leader was setting a fast pace, covering three-quarters of a mile in 1:10 3/5 on the sloppy track. Sunny's Halo didn't have any dramatic excuse, but his trip was sufficiently difficult that he finished behind three of the rivals he had soundly beaten at Churchill Downs.

Now that the reputation of Sunny's Halo has been shown to be slightly spurious, Deputed Testamony is the cynosure of the racing world. Bred and raised in Maryland, trained and ridden by Marylanders, he has become a local hero. And yet . . .

Deputed Testamony had everything go right for him on Saturday. If the easiest kind of trip for a horse is to take the lead and set a slow pace, the second easiest is to sit behind leaders setting a fast pace and slip through along the rail when they are weakening. With the expert guidance of jockey Donald Miller, that is exactly what Deputed Testamony did.

After Desert Wine had set the pace, discouraging several early challengers, he began to tire and drifted away from the rail on the turn. Deputed Testamony had been saving ground all the way, stalking the leader, and when the hole opened he shot through. Miller could not have dreamed of a better trip.

I have liked Deputed Testamony as a racehorse all spring; I loved the way he won the Tesio Stakes at Pimlico last month. But his triumph in the Preakness proved only that he is good enough to beat the country's best 3-year-olds when everything goes his own way.

It is still premature to get too excited about him. But three weeks from now, in the Belmont Stakes, he should have the opportunity to show whether he can win under normal conditions--just as Sunny's Halo had his chance to prove his legitimacy at Pimlico on Saturday.