NEW BRUNSWICK, N.J. — The woman behind me was talking about her memories of McCarthyism, and I assumed she must be speaking of her childhood.

But as I eavesdropped before the show at the New Brunswick Performing Arts Center, I heard her mention that she was 94. She had never liked the red-baiting Senator Joseph R. McCarthy, she said. She had been a fan, though, of his colleague and adversary Margaret Chase Smith.

“Conscience,” Joe DiPietro’s new comic drama, displays a similar allegiance in recounting the fraught events of seven decades ago. A timely boxing match of a history play, it stars a deliciously piquant Harriet Harris as Smith, the principled, moderate, junior senator from Maine who in 1950 publicly stood up to McCarthy when most of their fellow Republicans were too cowed.

In David Saint’s George Street Playhouse production, “Conscience” portrays Smith — the first woman elected to both houses of Congress and, at the time of the play, the only female senator — as a dry-witted hero with the rare courage to take on a lying bully who is sowing chaos, ruining reputations and threatening the very fabric of the nation.