Last night the Ripon Society, which former attorney general John Mitchell once called a bunch of "little juvenile delinquents," bestowed its leadership award on Rep. Guy Vander Jagt (R-Mich.), former Republican National Committee chairman Bill Brock, and Sen. John Heinz (R-Pa.). The society, a moderate Republican policy group founded in the early '60s by a group of Harvard and MIT graduate students, and its magazine, Ripon Forum, often have prickled the skins of Republican party leadership. But last night seldom a disparaging word was heard about Reagan administration policies, and either everyone was on his best behavior or, as one member of Congress put it, success has spoiled the Ripon Society.

"Anyone want a jelly bean?" asked Heinz last night of the roomful of Republicans, most of whom were still elated over November's victories. "Come on," he urged. "These aren't Communion wafers!"

Vander Jagt, Brock -- now U.S. trade representative -- and Heinz are credited with having masterminded the national strategy that brought their party, as Vander Jagt said last night, "from the courthouse to the White House," and to a majority in the Senate. The architects of success walked away from the podium cradling shiny silver bowls filled with jelly beans.

"I accept this award on behalf of the American people," said Vander Jagt grandly from the podium, "who, for the first time since 1952, voted Republican '. . . For a Change.'"

"Here, here," said several in the crowd, which included senators Charles Mathias (Md.), Ted Stevens (Alaska), Larry Pressler (S.D.) and representatives Millicent Fenwick (N.J), Tom Petri (Wis.) and Jim Leach (Iowa).

"'For a Change,' was the party's advertising theme," said William Baroody, Brock's executive assistant, who accepted the beans and bravos for his boss. "They spent $10 million on that. It worked."

Recent victories aside, there was still the society to think about last night, and while many were sanguine, some were not.

"I guess the question now is whither goest Ripon," said society president Richard Salvatierra. "We were sort of schizophrenic during the Carter years, and many of our members worked for John Anderson. The pendulum has swung, perhaps a little to one side, but the mandate's there."

"Moving from Cambridge to Washington was a fundamental mistake," said Petri, a founding member who calls himself the society's in-house dissident. "They've gotten into short-term tactical politics; too many of their people's salaries are dependent on the well-being of politicans like me."