It is a phenomenon that defies logical explanation, but sometimes the Saratoga track becomes so speed-favoring that front-runners never seem to get tired.

That is what happened two years ago, when the stakes races here produced a string of stunning upsets. After the sprinter A Phenomenon led all the way to win today's 1 1/8-mile Jim Dandy Stakes, it seems safe to conclude the bias has reappeared.

The colt had never run farther than seven-eighths of a mile, and trainer Angel Penna Jr. conceded, "I was really worried whether he could go the distance." But on this race track he could, and he held on to win by a head over Timeless Native in this prep race for the Aug. 13 Travers Stakes.

The outcome discouraged the Travers aspirations of the even-money favorite, Au Point, who collapsed to finish last, and the 5-to-2 second choice, Exile King, who was sixth.

There was no surprise in the way the early stages of the Jim Dandy developed. "I was going to the lead regardless," said A Phenomenon's jockey Angel Cordero Jr., who has always appreciated the importance of speed on this racing strip. So he did just that, as Au Point and a couple of longshots stalked him.

Au Point is a confirmed front-runner himself and, unable to get the lead, he dropped far out of contention. Timeless Native, a colt trained by Bud Delp, challenged the leader on the turn. But A Phenomenon held onto his narrow lead throughout the stretch--just as Island Whirl had done in Saturday's Jim Dandy Stakes--and lasted to win in 1:49 2/5. He paid $11 to win.

Given the nature of the track, the most impressive performance in the Jim Dandy was that of 30-to-1 shot Head of the Native, who trailed the field early, was running next to last turning into the stretch, and then accelerated strongly to finish third, less than a length behind the winner. He might be a more formidable Travers contender than either of the colts who beat him.

"He is nominated for the race," trainer Jonathan Sheppard said, "but I don't think he is quite ready for that, unless the field is not too big. We'll have to wait and see."