After attending the Breeders' Cup last November at Hollywood Park, Jim McKay was flying back home when he had the first glimmerings of a brilliant idea.

"It had been such an exciting day, with great fields of quality horses, that I was exhausted," the ABC sportscaster said. "On the plane home, I was trying to think of something like it to help the renaissance of racing in Maryland."

McKay has a small-scale breeding operation on his farm in Monkton, and he conceived the idea of a mini-Breeders' Cup for Maryland horses. He mentioned his idea to a few prominent people in the state's thoroughbred industry, and it generated a remarkable amount of momentum. Today, at a press conference at Pimlico, racing officials announced plans for the Maryland Million -- a one-day extravaganza with $1 million in purses spread over nine races for offspring of Maryland stallions. It will be run for the first time in the fall of 1986, and will be held at Laurel and Pimlico in alternate years.

The Maryland Million will raise money for purses in much the way that the Breeders' Cup does. Breeders will pay one-fourth of a stallion's stud fee to make his foals eligible to compete (with a minimum payment of $500 and a maximum of $5,000). Owners will pay $250 to nominate individual horses. James Lewis, president of the Maryland Million Committee, said that these sources would generate as much as $600,000; the rest of the money could come from corporate sponsorship of races, from the tracks and from a percentage of the wagering on the day's races.

McKay initially had discussed his idea with trainer Billy Boniface, with Pimlico's general manager, Chick Lang, with breeder Kimball Firestone -- but always with a bit of trepidation. He remembered the days when Maryland racing was insular and conservative.

But McKay found that an optimistic new spirit was beginning to prevail in the state -- fostered by the racing bill passed in Annapolis, by the aggressive new management at Laurel Race Course and other factors. "This was the right moment for it," he said. "Everybody I talked to seemed slowly struck by the thought: 'I can't see anything wrong with that.' "

As the 18-member Maryland Million Committee starts to make its plans specific, carpers probably will find plenty of things about the program that need changing. (Shouldn't there be a grass race for older horses? Shouldn't Maryland-bred horses by out-of-state sires be eligible? Aren't high-priced stallions such as Northern Dancer getting into the program too cheaply?) But the fact remains that this is a bold, innovative, exciting idea, one that every other state will be watching with interest.

"This is going to be a benefit to everybody -- to breeders, owners, trainers, jockeys and the tracks," McKay said. He should have added racing fans to his list, too. Most programs designed to foster state breeding industries have offered inflated purses for inferior races limited to state-bred horses. They have subsidized mediocrity. But if the Maryland Million works half as well as its creators hope, it should be one of the most exciting days of the racing year.