In his new memoir, Reporter, investigative journalist Seymour Hersh describes at least one story he regrets not reporting—an allegation that Richard Nixon hit his wife.

Shortly after Nixon resigned on August 9, 1974, Hersh got a tip that Nixon’s wife, Pat, had visited the emergency room alleging that the former president had hit her. In his memoir, Hersh admits “he made a mistake by not reporting this at the time,” according to a New York Times article about the book. Nixon’s family has not yet responded to this specific allegation.

This isn’t Nixon’s first allegation of domestic abuse, or even the only one that Hersh said he heard about during his career. In 2000, journalist Anthony Summers revealed in The Arrogance of Power: The Secret World of Richard Nixon that many reporters had heard stories of Nixon beating his wife, specifying Hersh had learned of at least “three alleged wife-beating incidents” from his sources.

One of the most credible accounts in Summers’ book comes from John P. Sears, a former Nixon campaign aide. According to Sears, Nixon family lawyer Waller Taylor “told me that Nixon had hit her in 1962 and that she had threatened to leave him over it … I’m not talking about a smack. He blackened her eye.” In addition to Taylor, Sears said that also heard the account from Pat Hillings, Nixon’s longtime friend and associate. (Nixon’s daughter Julie Nixon Eisenhower did not respond to the allegation in 2000, but she asked the director of the Nixon Library to respond on her behalf. He denied the accusation.)

Because of the intimate nature of domestic abuse, there are often no first-hand witnesses to the violence itself. And often, the victim is ashamed or afraid to reveal the abuse to others. In Pat Nixon’s case, her alleged abuse appears to have been an open secret among journalists, aides, and family friends. California Governor Pat Brown, Brown’s senior aide Frank Cullen, and reporter Bill Van Petten have all said that Nixon badly beat Pat around the time he lost the 1962 governor’s race to Brown. Van Petten also heard that aides like H. R. Haldeman and John Ehrlichman sometimes intervened to stop Nixon when he hit his wife, according to Summers.

In The New Republic’s review of Hersh’s memoir, writer Josephine Livingston describes how Hersh’s opinion of the 1974 allegation evolved over time. “He did not report on the story, he told Nieman Foundation fellows in 1998, because it represented ‘a merging of private life and public life,’” she writes. “Nixon didn’t make policy decisions because of his bad marriage, went the argument. Hersh was ‘taken aback’ by the response from women fellows, who pointed out that he had heard of a crime and not reported it.”

“All I could say,” Hersh writes in his memoir, “is that at the time I did not—in my ignorance—view the incident as a crime.”