Most of the time, gamblers deal with probabilities and narrow edges, not certainties. But every once in a while a betting man must screw his courage to the sticking post and declare: This is a cinch. I can't lose.

I will utter these words before the third race at Saratoga on Friday. Party King is a cinch, a three-star mortal lock. Although I am reluctant to bet the major portion of my bankroll on the third day of a 24-day meeting, the circumstances demand it.

Party King has been based in Maryland for most of the year, and at Delaware Park for the past month. Trainer Dick Ferris brought him to Saratoga principally as a traveling companion for his brilliant stakes horse, Star de Naskra, who is running in the $100,000 Whitney Stakes on Saturday.

$ party King has been running all year under conditions similar to those of Friday's third race, a $20,000 claiming event at 1 1/8 miles. On the surface his credentials do not appear particularly formidable: He has won only one of nine starts. But the $20,000 claimers he has been facing in Maryland have been an extremely tough, competitive bunch.

In each of his last two appearances at Pimilico, Party King finished second while being soundly beaten by a rival named Prime Hour. That name won't mean much to New York handicappers, but it will to Marylanders who know that Prime Hour put together a five-race winning streak, stepped into allowance company and beat rivals worth $40,000. On one of the occasions that Prime Hour beat Party King, he ran considerably faster than stakes horses did on the same day.

After the second loss of Prime Hour, Party King was laid off for a month and returned to competition at Delaware. He finished third against more tough $20,000 claimers. His next performance has undeniably sensational.

Trailing early, Party King caught the leaders at the top of the stretch and ran away from the field by seven lengths. His time for the 1 1/6 miles was 1:44 1/5. On the same day, an allowance race for some of the best horses at Delaware Park was run only three-fifths of a second faster.

If Party King's times suggest that he is more than a $20,000 animal, the times of the races of his Saratoga rivals indicate that they are worth less. The Daily Racing Form selectors' top choice, Deal With Strength, won his last start by a nose over a horse who had not been able to win for more than $10,000. His time was more like that of a $10,000 claimer, too.

It is possible to compare with some precision the times of horses who have run different distances at different race tracks. While the speed-figure methodology is somewhat complex, the results in this case are unequivocal. They suggest that Party King's normal performance is about five lengths better than the best recent races of all his Saratoga rivals.

If this race were being run in Maryland or Delaware, Party King would be an overwhelming favorite. But New York racetrackers, like New Yorkers in general, usually look on out-of-towners with skepticism or contempt.

As a result, Party King ought to pay at least 2 to 1. It will take an act of God to beat him.