When I walked to the betting window to put a stack of $100 bills on Pearl Necklace at Belmont Park Wednesday, I felt like a moth being drawn ineluctably to a flame.

The mare was so superior to her opposition that I had advised readers of these pages to "bet the rent" without hesitation; I had encouraged friends to fly with me to New York and tap out on the race; I had solicited money from coworkers at The Post.And now I had the growing sense that I had blown it.

It's one thing to lose a race because of of an act of God, or some unforeseeable circumstance. This summer at Saratoga, I bet a horse who crashed through the rail in midstretch and wound up swimming in the infield lake, and I took that setback with manful stoicism. But if I lost this race at Belmont it would be for the worst possible reason: I had been guilty of an oversight; I had committed a gross handicapping blunder.

Pearl Necklace is a front-runner who had drawn Post Position One in the Maskette Stakes. She would have no choice but to battle for the lead along the rail. This would have been an advantage for most of the Belmont meeting -- at least until last Saturday, when the track began to change.

Since that day, speed horses on the rail hadn't been able to win. Nearly every race at Belmont was captured by a horse who laid off the pace, swung to the outside and made a late rush in the middle of the track. Unfortunately, I had overlooked the evidence of this bias in the Belmont results, and the realization did not dawn on me until mind.

Pearl Necklace fought for the early lead, as expected, and opened a narrow lead at the top of the stretch. But when a long-shot named Blitey started to circle the field and charge down the middle of the track, I knew I was doomed. Even before the horses had crossed the wire, I was thinking of the headline in The Post that morning and asking myself: Why do I invite such public humiliation?

The reason is that I'm not satisfied just to make money when I pick a winner; I want glory, too. There is, however, a strict race track rule of etiquette that says you may not gloat about a winner after the fact unless you have announced your opinion beforehand. As a result, I am a compulsive tout. I am forever foisting my ideas onto my race-track cronies. Back in high school, I used to take up collections from students and teachers to bet on my hotskis at Randall Park.

But what grander scale is there for touting than to advise a newspaper's entire readership about the existence of a mortal lock? When I trumpeted the virtues of Party King at Saratoga last month, and he paid $9.60, I received telegrams, profuse congratulations, proper recognition as the World's Greatest Handicapper. It only occured to me dimly to wonder what would have happened if he had lost.

Now I know. One of the worst parts of the whole experience is Breaking the News. After the Earl Necklace race, I was instructed to call my sports editor's office where a group of anxious toutees would be waiting by the speakerphone. I could only babble contrite apologies. It would be easier to break the news of a death in the family.

Then there were the inevitable tales of woe. "Will you tell my kids they can't go to camp next summer?" one coworker asked. He was kidding. The friend who said he had flown to New York to bet $1,000 on the horse wasn't.

Another friend told me, "You really did it this time. All the people who were kicking themselves because they didn't get down on Party King were lining up to bet this one. Thanks. I owe you a dinner." That friend, of course, was a bookmaker. At least I made somebody happy.

But the worst part of the Pearl Necklace experience has been answering the inevitable question, "Why did she lose?" I wish I could chalk the defeat up to the inscrutability of the game, but I can't. I have to confess: I was guilty of handicapping malpractice.

It won't happen again. The next horse cited here as a mortal lock will be just that.