Terry Leibel on the Merchant of Venice took a chance that paid off handsomely last night at Capital Centre, scoring 1,500 points in 60.36 seconds to win the $5,000 Gambler's Choice class at the Washington International Horse Show.

Points are assigned each jump on the basis of difficulty. Each rider is given 60 to 90 seconds to choose his course and accumulate a score for each jump cleared. The rider with the highest score in the fastest time is the winner.

Leibel, 26, of Willowdale, Ontario, was the ninth to go in a field of 26 international riders. Each had a choice of 12 jumps to negotiate.

"I tried to pick up as many high point fences as possible as quickly as possible," said Leibel. Her horse, Merchant of Venice, is a 16.2 hand, aged bay gelding.

Cindy Carlson of Ann Arbor, Mich., on Ruth Everett's chestnut gelding Cheers finished second with 1,340 points in 64.04.

The win for Leibel, who has represented Canada in international competition, boosted her into third place with 15 points in the national rider standings behind Dennis Murphy with 17 and Bernie Traurig, 16.

Walter Gabathuler, representing Switzerland finished third with 1,320 point in 64.27. The win for Switzerland, considered to be the longshot in the team competition, tied it for first place with the United States Equestrian Team with 34 points. Tonight's $25,000 President's Cup Grand Prix will be the deciding event.

Terry Rudd on Semi-Tough, the last competitors to ride in the Gambler's Choice last night, were fourth with 1,310 in 63.60.

Leibel was riding her "back-up mount." The horse she said, is of questionable breeding. It is by her request that she didn't represent her team because she will ride a new horse, Volunteer, in tonight's grand Prix. Volunteer is an 11-year-old chestnut gelding.