A lot of would-be congressmen try to act holier-than-thou, but Barney Frank will have to watch his step -- he's running in the Democratic primary to replace Robert Drinan. That's Father Robert Drinan.

Friends, family, supporters and old college roommates joined Frank, 40-year-old Massachusetts state representative, yesterday evening at a fund-raiser held in the Market Gallery. Many of his backers in Congress had to miss the reception because of Ted Kennedy's thank-you dinner in McLean for congressional supporters. But it didn't seem to dampen Frank's good humor. Not the man whose 1972 campaign poster, displaying a photo with George McGovern, asked, "Who's That Man with Barney Frank?" Not the man whose 1974 poster, showing him disheveled, read, "Neatness Isn't Everything -- Reelect Barney Frank."

"Sixty-six percent thought I had a good sense of humor," he said, confiding the results of an apocryphal poll during a break from gladhanding contributors and lighting up cigars. A much higher percentage at the reception thought he'd made a hell of a congressman.

"He's a close-to-perfect, replacement," said Joseph Rauh, "Mr. A.D.A." as one member of the organization called him. "Barney's better than anyone I know at convincing people in public life that doing the right thing is in their own interest," added Ann Lewis, administrative assistant to Rep. Barbara Mikulski (D-Md.) and Frank's sister. She also recalled his more-than-casual interest in politics while in college: "You need 16 courses to graduate from Harvard. Barney took 17 -- they were all political science."

Charlie Halpern, a roommate at Harvard and now a professor of law at Georgetown, remembers showing up at Harvard proud about knowing "that there were two houses in Congress." Frank quickly bet him that he could write down the names of 50 members and over 400 congressmen. "He had the names," says Halpern, though he's still not sure if they were the right ones.

Last Saturday, Drinan announced his support for Frank in the four-way primary race to be decided September 16. They traveled together around Drinan's Fourth Congressional District. That, said Frank, reopened some of the pain for the priest, ordered out of Congress by his pope. "He didn't agonize over the decision," observed Frank, "but it anguished him."