Jim McKay, the ABC sportscaster, has witnessed the thrill of victory and the agony of defeat in countless sports and in countless exotic locations. But one event that stirred him as much as any was a run-of-the-mill horse race at Pimlico this summer.

McKay and his wife are part-owners of a filly named Heartful Star, and as he watched her draw away through the stretch to win by more than five lengths, McKay could hardly believe how he was affected.

"Going to the winner's circle that day was one of the greatest thrills I've ever experienced," he said. "A couple of days later, I made a hole in one -- the only time I've ever come close -- and I had a chance to compare the two. Going to the winner's circle was the bigger thrill, and I wondered why. After all, Billy Boniface had trained him and recommended I buy him; the groom groomed him and the jockey rode him. Maybe it's like the feeling you have when your own child accomplishes something."

Whatever the reason, McKay is hooked on the sport, and his enthusiasm might have a lasting effect on Maryland racing. Last fall, he conceived the idea of the Maryland Million, a nine-race program offering $1 million in purses for the progeny of Maryland stallions. He talked about the concept to track officials, breeders, trainers and owners throughout the state, and enlisted widespread support for it. Last week, he presided at a press conference at Pimlico in which plans for the Maryland Million were formally announced.

McKay's interest in thoroughbred racing goes back a long way. "The first television show I ever did was 'Racing from Pimlico' in 1947," he said. "On 'Wide World of Sports', we did most of the great races in the world. But it was when ABC got the Derby and the Preakness that my interest really started to grow.

"My wife Margaret and I had been thinking for years of leaving New York and reestablishing our Maryland roots -- she's from Baltimore and I moved there when I was 14. She wanted to go, but I'd say, 'What'll we do? Twiddle our thumbs in Guilford?' But when I started thinking about raising horses . . . "

The McKays bought a farm in Monkton, starting a modest breeding operation. Their beginning was even more modest than they might have expected. "In 1980," McKay said, "we went to the Keeneland fall yearling sale with $10,000 clutched in our fists. We were there for three days and looked at 150 horses, and every time we bid they went past us. My wife finally said, 'I thought this was supposed to be fun.' Finally, though, we bought a filly."

The McKays named their acquisition Special Darling, and the filly provided her owners with a rude introduction to the realities of the game. She bucked her left shin five times, her right shin twice and never accomplished anything. The McKays had to wait four years until they finally won a modest race last fall.

Undaunted, they enlarged their operation, and they now have on their farm three pregnant mares, two yearlings and two weanlings. They are fired with enthusiasm. "At our age," McKay said, "I think it's great to have a brand new interest."

McKay cherishes the hope of any small breeder: to raise a horse who wins a stakes race. He will occasionally let himself dream an outlandish dream of winning the Kentucky Derby or the Preakness. This is improbable, of course, but McKay is going to see at least one improbable vision take form when the Maryland Million becomes a reality next fall.