Proud Truth accelerated powerfully in the final yards to win the $300,000 Florida Derby today.

Ordinarily, such a victory would immediately give great credibility as a Kentucky Derby contender. But Proud Truth was actually upstaged despite his neck victory over Irish Sir.

Earlier in the afternoon, the 2-year-old champion of last season, Chief's Crown, returned to competition and won the seven-furlong Swale Stakes. And the performance of Chief's Crown didn't compare with that of another 3-year-old, Rhoman Rule, who started his campaign with a smashing 10-length victory in an allowance race.

But for the time being, the headlines will belong to Proud Truth, the classically bred colt from Darby Dan Farm. This was his fifth victory in a six-race career that started only last December, and although his time of 1:50 for the 1 1/8 miles was distinctly mediocre, he at least accomplished it with dramatic flair.

Because there was relatively little speed in the 11-horse field, jockey Jorge Velasquez knew he couldn't permit Proud Truth to drop too far behind the leaders. So while Banner Bob and Mighty Appealing raced head and head for the lead, setting a slow pace, Proud Truth stayed in the middle of the pack.

On the turn, Banner Bob was beginning to weaken and Mighty Appealing was beginning to collapse. As they faded, Proud Truth and the even-money Stephan's Odyssey drove through along the inside, and Irish Sur made a strong four-wide move.

Irish Sur and his brilliant young jockey, Jose Santos, looked momentarily as if they were going to win, especially as Velasquez found himself trapped on the rail behind the tiring Banner Bob. But when Proud Truth found a little daylight, Velasquez said, "He took off like a wild horse."

He drove between Banner Bob and Irish Sur and outfinished the latter, who is himself a strong closer. His trainer, John Veitch, exclaimed, "That showed his real character and ability."

Yes, but the slow clocking of 1:50 confirmed the growing evidence that the stakes horses who have been racing here this winter are a very undistinguished lot.

In even a run-of-the-mill year, a 3-year-old who goes so slow would be considered a marginal contender at best.

If Proud Truth wasn't overwhelming, the horses behind him were even less so. Irish Sur did run well, losing so much ground on the turn. But the highly touted Stephan's Odyssey had no excuse; Banner Bob showed conclusively that he can't go 1 1/8 miles, and the Maryland colt, Mighty Appealing, wound up in oblivion. He finished 10th, more than 20 lengths behind the winner, and was able to beat only a 138-to-1 shot who didn't belong in the field.

Chief's Crown didn't run dazzlingly fast, either, but his time of 1:22 2/5 for seven furlongs was at least respectable and he looked good doing it. Certainly, he laid to rest the rumors that he has one hoof in the grave. He raced five-wide down the backstretch, shook clear on the turn, and then ran away from a stakes-class stretch-runner, Creme Fraiche, through the lane.

But the most eye-catching performance of the day came in a low-grade allowance race. Rhoman Rule was facing a good field that included one of Woody Stephens' good speedsters, J.O.'s Best, who sped the first half-mile in 44 4/5 seconds. As he did, Rhoman Rule was stalking him, even though Jacinto Vasquez hardly asked for a response. Then he left the leader for dead and drew away, hitting the six-furlong mark in 1:09 1/5 and covering the seven-eighths in 1:22, two-fifths of a second faster than Chief's Crown.

The time was vastly more impressive than that of the Florida Derby. Proud Truth, watch out.