Bet Big scored an upset victory in the Preakness Prep today and tarnished the credentials of three candidates for next week's classic at Pimlico.

He beat a lightly regarded filly, Lovin Touch, by one length, as Noble Home, Dixieland Band and Assault Landing all turned in unexpectedly mediocre performances.

"How can you not run in the Preakness now?" owner Ben Cohen asked rhetorically after his colt's triumph. In fact, Bet Big has never indicated that he has the stamina to win at the Preakness distance, but his presence will very likely change the complexion of the race. Before today, there was no speed horse in the lineup who figured to pressure Sunny's Halo and Desert Wine, the one-two finishers in the Kentucky Derby. Now there is.

Bet Big did not break sharply from his outside post position, but rushed up and was forced to race three-wide around the first turn, an often fatal disadvantage at Pimlico.

He dueled with Noble Home down the backstretch, covering the half-mile in 47 seconds and the three-quarters in 1:11, when it seemed that the stretch-runners were about to make their moves. They didn't. Assault Landing, the 3-to-5 favorite, never accelerated.

Instead, Bet Big took command turning for home and was never seriously threatened in the stretch, as he covered the 1 1/16 miles in an unsensational 1:43 1/5. "He won with plenty in hand," jockey Roger Velez said. "He could have run around twice today, and they still wouldn't have caught him."

Actually, Lovin Touch probably would have caught him if she hadn't had such a difficult trip. Julie Krone was forced to check the filly sharply entering the backstretch and steady her again approaching the final turn. She was probably the best horse in the field, and she established herself as a strong contender for next Friday's Black-Eyed Susan Stakes.

In the feature race, the $115,500 Dixie Handicap, Vincent Bracciale Jr. brought Khatango from far behind to score a 2 3/4-length victory over London Times, with Super Sunrise third.