Ernest Lefever, the Reagan administration's controversial nominee for assistant secretary of state for human rights, got grilled at the Cosmos Club last night. Of course, he was expecting it, and the proceedings were mild compared to what he can expect from his Senate confirmation hearings in a few weeks, but that didn't make it any less grueling.

"How did I do?" he said after about 30 minutes of questions from a group about equally divided between Lefever fans and skeptics. "Did I fall on my face?" The real question was whether the evening, organized to allay misgivings over Lefever's nomination, succedded in winning him any new supporters. At evening's end, the verdict on that one was still out.

"I believe," said Lefever in response to one question about the Carter administration's approach to human rights, "we are more effective through private pressure and private arm-twisting." He later attributed the release of three of several human rights leaders arrested over the weekend in Argentina to "high-level" arm-twisting by the Reagan administration.

"He's wrong," said Father Robert Drinan vehemently after it was all over, "all wrong." Drinan is a former congressman from Massachusetts, now a professor at Georgetown Law School and a prominent human rights activist.

"Once he takes office," said U.S. Ambassador at Large Max Kampelman, "you'll find no one with a greater commitment to human freedom and dignity. There is no doubt he will serve with distinction."

Others in the crowd were former SALT 11 negotiator and deputy secretary of defense Paul Nitze, the American Jewish Committee's Hyman Bookbinder, Howard University law professor and former assistant attorney general Wiley Branton, and newsman Martin Agraonsky. U.N. Ambassador Jeane Kirkpatrick and Sen. Henry Jackson (D-Wash.) didn't show. And then there was one man present who, apparently unwilling to be associated with the Lefever cause, insisted he was not. "I'm really not here," he said with feeling.

The cocktail party and impromptu "Ernie bee" (as one guest dubbed it) was hosted by Kampelman, an old friend of Lefever's and co-chairman of the U.S. delegation to the Madrid Conference on Security and Cooperation in Europe. But Lefever's Ethics and Public Policy also made some phone calls and issued a few invitations.

"I've known Ernie for 20 years," said Kampelman in his introduction. "Even in those early days he had a tendency to overstate his views.

"It did not surprise me," Kampelman continued, "when I learned in Madrid that Ernie's nominatin did not bring universal joy . . . I read some of his materials on the plane, and underlined some sentences, and marked them with X's. And if you don't ask the tough questions, I will."

They did. There was a question about U.S. support for South Africa in view of its "horrendous racial policies."

"My view," said Lefever, "is that all countries should be treated approximately the same. We have relations with the Soviet Union, where people are brutalized every day. . . ."

He was asked about arms negotiations with Russia. "We should arrive at a sufficient posture of strength" before negotiating, said Lefever. Does that mean more arms buildup before any negotiations, does that mean you believe we are weaker than the Soviet Union, the same questioner continued" "You're putting words into my mouth," Lefever began. "I'm not putting words into your mouth," interrupted the questioner, "I'm trying to figure out what you mean."

"I'm learning," said Lefever, after declining to answer a specific question on human rights. "I was just briefed by our legal department. I hit the ground crawling."