When it comes to the politics of sexual scandals, there’s an iron-clad rule that Clarence Thomas’s handlers recognized implicitly, which Herman Cain may be about to pay the price for breaking: Two women is company, three’s a crowd. Four, which is the number who have now accused Cain of inappropriate sexual behavior, is a farewell chorus.

I’ve been debating with colleagues for the last week whether the allegations against Cain would be lethal to his Presidential aspirations. As someone who spent three years investigating and reporting on Anita Hill’s allegations against Clarence Thomas for the book I co-authored with Jill Abramson, “Strange Justice,” I argued from the start that anyone who believed this wouldn’t hurt Cain didn’t understand the political dynamics of sex scandals. Of course, supporters rally emotionally to the defense of the accused. They decry the unfairness of the media. They try to undermine the credibility of the accusers in every way they can. But if the accusations are believable, the American public will not be forgiving. And nothing makes alleged sexual misconduct more believable than a pattern of behavior, formed by multiple accusations.

It was for this reason that nothing was more important to Thomas’s sponsors during the Senate confirmation hearings than suppressing the testimony of other women with stories that were similar to Hill’s. There were three such women who were willing to speak out, and Thomas’s supporters knew he would not have had much of a chance if they had been allowed to do so. Although Thomas famously decried his mistreatment by the Democrats as a “high-tech lynching,” in truth, neither the Democrats nor the Republicans wanted to be blamed for killing his confirmation under such controversial circumstances. Rather than giving the women their say, the leaders of both parties kept them from the limelight.

Angela Wright, who, like Hill, had worked for Thomas at the Equal Employment Opportunity Commission, spent the hearings holed up in a motel across the Potomac River in Northern Virginia. She had come from North Carolina to testify that she remembered Thomas making inappropriate sexual remarks in the office to the women who worked for him, such as asking Wright what her bra size was, and talking about how sexy he found her unshaven legs. As she waited, the hearings were gaveled to a close without the public or members of the Senate ever having the opportunity to hear from her. (Instead, her statement was entered into the public record, later.) Rose Jourdain, an elderly speechwriter for the E.E.O.C., was able and willing to corroborate Wright’s account. She was recovering from surgery in the Washington Hospital Center at the time, but had still been willing to testify, even if she had to be rolled into the hearings in a wheel chair. Instead, she, too, waited and waited but was never called. She has since passed away. Sukari Hardnett, a former Special Assistant at the E.E.O.C., was relegated to submitting a written statement accusing Thomas of treating women on his staff in “odd but not egregious” ways that she found “inappropriate.” No persuasive reason has ever been given for why these women should have been denied a chance to testify. In the intervening twenty years since the Hill-Thomas showdown, however, two former Senate aides, both Democrats, have admitted privately that their bosses knew that Thomas would have been unlikely to survive multiple accusers. Facing this moment of decision, they flinched.

Cain, as a Presidential candidate, has been the subject of the free-for-all of a 24/7 media circus, and so hasn’t had the luxury of controlling the message, or number of accusers, so neatly. (Iowans are reportedly having second thoughts.) His handlers do, however, seem to be following one page from Thomas’s successful survival playbook: When accused, take the position advocated by an aide to former South Carolina Senator Strom Thurmond, who was one of Thomas’s chief sponsors. When asked how Thurmond would react, after reading a four-page detailed statement of Hill’s allegations, the aide predicted without a moment’s hesitation what the Senator’s response would be: “Categorical denial.” (“All allegations of harassment against Mr. Cain are completely false,” Cain’s campaign said in a statement Monday. “Mr. Cain has never harassed anyone.”)

Above: Anita Hill takes oath before the Senate Judiciary Committee on October 12, 1991. Photograph by Jennifer Law/AFP/Getty Images.