When the horses turned into the stretch in the second race at Gulfstream Park Thursday, I had the opportunity to yell something I have yearned to yell in two decades as a bettor:

"I win 10 thousand!"

If that noisy pronouncement represented a slight breach of race-track etiquette, I felt entitled, for the victory of a longshot named Joanne's Choice was my payoff for weeks of hard work and study. It was a triumph of virtue.

Before I had come from Washington to Gulfstream, I had spent many long nights analyzing the records of the trainers who would be racing here. I maintained index cards for more than 100 of them, noted the circumstances of all their winners, and then analyzed the data looking for men with reliable modi operandi.

One of the names on my list was an obscure trainer named Kenneth Kemp, who had managed to saddle at least one implausible longshot winner every winter in Florida. When I spotted Joanne's Choice in the entries for Thursday, he looked sufficiently implausible. He had not raced for five months, and had lost the only two starts of his career by 17 and 19 lengths.

If Joanne's Choice were a hotski, I figured Kemp would be betting his horse in the daily double, and so before the first race I stood by the closed-circuit television monitors and charted the fluctuations of the double prices.

Joanne's Choice was being completely ignored until two minutes before post time, when all the prices involving him suddenly plummeted. Combinations that had been paying $800 were now paying $600. This was not unequivocal stable betting, but on the chance that it might be significant, I dashed to the windows and played a pair of $40 daily doubles.

One of my horses won the first race at 6-to-1 odds, and when the probable double payoffs were posted, I saw that the combination with Joanne's Choice was worth $524.40. My $40 ticket could be worth $10,484.

I restrained my excitement, remembering that Joanne's Choice had never run decently in his career. But when he went to the post at surprisingly low odds of 15 to 1, I suspected I had a live horse. When he broke sharply and was practically pulling jockey Roger Danjean out of the saddle along the backstretch, I knew.

Joanne's Choice cruised toward the two leaders, Upset Plenty and Cats And Dogs, and swooped by them on the turn. When he opened a clear lead turning for home, I saw that nobody else was making a move at him and I knew I had a winner. The official margin of victory was 7 1/2 lengths.

As I accepted congratulations from press-box friends and expounded on the way I had handicapped the double, I was too preoccupied to notice that the red OBJECTION sign had noted on the tote board and the number 11 -- Joanne's Choice's number -- was blinking. My reverie was finally interrupted when the public address system said that the rider of the fifth-place finisher, Cats And Dogs, had claimed foul against the winner.

I felt a sense of deja vu as I watched the patrol films on the press box television. There is a jagged aperture in the wall by that television and a sign above it reading BEYER'S HOLE, which I had bashed two years ago after suffering a costly and illegitimate disqualification. But as I watched the films this time, I saw that the foul claim was legitimate. Joanne's Choice had cut in front of the other horse as he passed him on the turn, making his jockey check him sharply.

Suddenly, the tote board went blank, the crowd roared, and Joanne's Choice's number came down. I headed directly to the clubhouse bar to belt down a double shot of Jack Daniel's, ruminate upon the cruelty of fate and think about the $10,000 that might have been.