The long spate of social events preceding the even long Washington International Horse Show was off at a moderate gallup last evening. One hundred fifty equine enthusiasts who were fortunate enough to get their money in early ("We've had to turn people away from all of the events," said a spokesman for Margaret Hodges, who is chairman of the social activities) paid $175 apiece to gather at the home of OAS Secretary General Alejandro Orfila to eat turkey, and ham and shrimp and meatballs and beef and cheese, and talk horse.

Plans for this year's show at the Capital Centre, which starts this Sunday and runs through Oct. 28, are of the bigger and better variety: more prize money, a challenge purse to break the North American puissance (high jump) record, Lippizaner dressage exhibitions, Budweiser Clydesdale exhibitions, a Western Night and parties, parties, parties. But the conversation at the kick-off social event tended toward the small. Horses, that is.

Hermen Greenberg, who was being philosophical about having to move his racehorses from Laurel to Pimlico because of track difficulties, was more interested in talking about the miniature horses he is breeding on his Leesburg, Va., farm. "You should see one I have, only 29 inches high and the perfect confirmation of a thoroughbred." His wife, Monica, who was musing about the possibility of housebreaking a couple of them, said, "Our place is only 10 acres.I tell people we need miniature horses because we have a miniature farm."

Orfila, who imported some of the first miniatures from his native Argentina-(where they were developed)-to the United States some years ago, also concentrated on the less than monumental. "Oh, I don't want to talk about work tonight," he said when asked about the El Salvador situation. "Let's talk about horses." And other than to say that he is "optimistic... optimistic by nature," in reference to the recent coup in that Latin American country, he did indeed focus on horses.

"Hey, where's the Pressler for President button?" Sen. Larry Pressler (D-S.D.) jokingly asked OAS protocol chief Manuel Ramirez, but that was the extent of that frequent partygoer's politicking. He, like everyone else at last night's event, had a good reason to be there. "I ride a little bit, but Western, of course. And I'm chairman of the Capitol Hill Equestrian Society."

Another political equestrian was Joseph Tydings, who as then senator from Maryland enacted legislation protecting the Tennessee walking horse some years ago and became something of a hero to humane societies as a result. His interest goes back even further.

"I grew up with horses and I was in the last horse cavalry in the U.S. Army-Patton resurrected mounted cavalry in the army of occupation and I transferred as soon as I could."

When asked whether the former cavalryman missed the campaign trail, Tydings' response was a yes, but. "I get pleasure from helping get good candidates elected to office. Right now we have two very good senators from Maryland, and I come frome the school that believes you don't run against good incumbents."