Is some sort of mass psychosis afflicting people who bet on horse races in Maryland? Characterized by delusion and loss of judgment, it might be termed Pradomania. The sufferers evidently believe that jockey Edgar Prado is capable of performing miracles.

Prado, of course, is the state's dominant jockey and the nation's top race-winning rider. He possesses exceptional skills, and he gets his choice of the best mounts, too. Accordingly, bettors have always backed his mounts enthusiastically. But lately, this enthusiasm has bordered on lunacy.

The way bettors view Prado raises a basic question about the game: How important is the jockey as a factor in handicapping?

Of course, if everything else were equal, any rational person would prefer to have his money on Prado than on a jockey with lesser skills. But everything else is not equal. Jockeys recognized as the best in the profession, or the best on their racing circuit, are bet accordingly, and the odds on their horses are depressed, so there is no edge playing them. As they would say on Wall Street, the market has discounted the jockey factor.

The best rider in America is Jerry Bailey, and at the current Belmont Park meeting he has been winning at an exceptional rate: 28.9 percent. (Riders never win as much as one-third of their races over a lengthy period.) But Bailey's skills have been fully discounted on the tote board. According to statistics in the Daily Racing Form, the average payoff on his winning mounts has been a meager $6.01. Betting all of his horses would have produced a 13 percent loss. A lesser jockey will blow a few races that someone of Bailey's caliber might win, but the higher payoffs will compensate for them. Therefore, I'll usually make my bets regardless of the jockey -- unless I regard him as a total incompetent.

There is only one situation in which I will pay special attention to jockeys: when a strong bias is dictating the outcome of races at a particular track. Certain riders are adept at spotting biases and will adjust their horses' style to take advantage of the conditions. (Angel Cordero Jr. was the master of the art.) Some jockeys have styles that may or may not suit a biased track. Mark Johnston is a member of the take-`em-back-and-go-wide school of riding, and he was a bad bet when Pimlico favored speed horses on the rail. But at Laurel, which has tended to favor off-the-pace runners, Johnston is winning with 20 percent of his mounts and ranks a close second to Prado in the jockey standings.

For many years, Prado's superiority has been an unavoidable factor in Maryland races. He outclasses his rivals so much that he frequently wins races on the second- or third-best horse, exasperating bettors in the process. So the odds on a horse should be depressed if Prado is in the saddle. If a horse deserves to be 3-1, he might justifiably go off at 2-1 with Prado aboard.

But lately, it seems to me, many of Prado's mounts have been overbet to the point that their odds bear no relationship to the horse's chances. Consider these examples of Pradomania in the past week:

Soul Survivor hadn't raced in 10 months, and his 1998 form was not exceptional. His trainer hadn't won a race in 1999. Bettors ordinarily might eliminate such a horse, but with Prado aboard they made him a 6-5 favorite. He finished last.

Woman's World's only victory in nine races came in a weak six-horse maiden $7,500 claiming race in Atlantic City. Now she was running against solid allowance-class horses at Laurel, the best of whom were worth $25,000. Completely overmatched, she deserved to be 20-1. Yet with Prado aboard she went off at 7-2 and finished sixth.

Lucky Trend finished last in his only two starts of 1999, losing by a total of 31 lengths. Even a sharp drop in class didn't figure to help him. Yet with Prado aboard, bettors made him an even-money favorite. He lost by nearly a dozen lengths.

Why are bettors displaying such irrational exuberance where Prado is concerned? The jockey has been in a mini-slump, by his standards, and maybe horseplayers keep figuring that he's "overdue." More and more betting on Maryland races comes from out-of-state simulcast customers, who are presumably less knowledgeable than the on-track regulars, and perhaps they are more apt to bet blindly on a big-name jockey.

In any case, the enthusiasm for Prado offers a useful handicapping lesson. A horseplayer who bet on all of Prado's Maryland mounts in 1999 would have had about the same return on his investment if had made his selections by throwing a dart at the Daily Racing Form. Even the best of jockeys do not deserve bettors' blind faith.