It was January, 1973, and the U.S. Supreme Court had just ruled in Roe v. Wade that abortion was not a crime. According the New York Times, Nixon made no public statement.
Privately he told Charles Colson, with whom he was chatting in the Oval Office; their conversation picked up by the infamous secret microphones:
"There are times when an abortion is necessary. I know that. When you have a black and a white," he told Colson. It was Colson who added the words, "or rape," with which Nixon readily agreed.
So there's Nixon in audio tapes from January and February 1973--released Tuesday by the Nixon Presidential Library--showing "ambivalence" about abortion--except for miscegenation or rape. Colson and Nixon seem to equate the two.
While Nixon was expressing an opinion that was probably widespread at the time, an 11-year-old boy named Barack Obama, whose mother was white and whose father was black, was growing up, raised mostly by his white grandparents.