Following Donald Trump’s presidential election, many commenters have debated whether his voters were motivated by racism or by economic anxiety. Sexism is rarely mentioned anymore. Yet Trump boasted on tape about sexually abusing women, and many accusers came forward to say he had groped them or harassed them. Nonetheless close to 50% of voters cast their ballots for him. Trump insisted his accusers were lying, and that was enough—millions of people decided these women’s testimony was inadequate or irrelevant.

In her new book Tainted Witness: Why We Doubt What Women Say About Their Lives, Leigh Gilmore, a visiting professor at Wellesley College, argues that public disregards for women’s testimony is an American hallmark. “Doubting women,” Gilmore writes, “is enshrined in the law, represented in literature, repeated in culture, embedded in institutions, and associated with benefits like rationality and objectivity.” She adds, that “the victim who is presumed to be complicit can never be pure enough.”

Gilmore points to the Clarence Thomas US Supreme Court hearings in 1991 as an iconic example of the way in which women who speak publicly are smeared and undermined. Conservative groups had worked for years to put Thomas on the court and he was finally nominated by former president George HW Bush.

Thomas’ smooth path to the bench was interrupted, however, by accusations from one of his former subordinates at the EEOC, Anita Hill. Hill said that Thomas had made lewd comments to her, pressured her for dates and sexually harassed her.

Hill did not ask to speak at the hearings. But she was subpoenaed, and then her sealed testimony was leaked to the press. Through it all, Thomas’ team successfully smeared her as a conniving woman out for publicity and revenge.

“I was cast as just another African American woman who was not to be trusted to describe her own experiences truthfully,” Hill later said. The committee assumed that women lie, and refused to listen to other witnesses who could have provided additional evidence of Thomas’ abusive behavior. As a result Hill, rather than Thomas, was effectively put on trial for Thomas’ actions.

People like Anita Hill and Trump’s accusers, Gilmore said via email, “are citizens who step into moments of great national consequence. They have the gratitude of many, and there is really no benefit to them beyond a clear conscience and doing a duty to democracy, but they get smeared.”

The smearing is accomplished through several mechanisms. First, Gilmore says, the narrative of women as tainted witnesses is activated through “amplifying doubt in the form of sexual blame, fault-finding, and outright slander.”

Trump did this in part by casting doubt on the women who accused him. But he also did so by attacking Hillary Clinton, suggesting that she was implicated in longstanding rape and infidelity charges levied against her husband Bill Clinton. ”Blaming Bill fit neatly with blaming Hillary,” Gilmore notes. “She was blamed for Bill’s affair with Monica Lewinsky—for allowing it to happen, for causing it through some marital failure, or for not divorcing him. In a situation in which any of those judgments can seem persuasive, then each specific judgment is less significant than the mobility of accusation itself and the rapidity with which judgment and blame sticks to women.” Men accused of sexual violence can deflect blame by tarring virtually any woman nearby with virtually any charge of impropriety. The details, and even the target, matters less than the fact that women are assumed to be sexual liars.

The second way in which women’s testimony is dismissed is through the use of a “he said/she said” frame. “He said/she said works partly because we are groomed to believe it is a reasonable, even admirably skeptical position to take when accounts differ,” Gilmore told me. “But it works to discredit women by creating the appearance of a false equivalence between a women’s experience of being assaulted and an assaulter’s actions.”

The focus on he said/she said tends to narrow discussion to only what he said and she said, eliminating other context and making all accusations of sexual violence or coercion vanish. In Hill’s case, the committee enforced the he said/she said structure by refusing to hear testimony of other relevant witnesses who could have confirmed her story. For Trump, the fact that he himself boasted about his sexual harassment was not enough to disrupt the narrative being pushed by surrogates.

Powerful men—Clarence Thomas, Trump, Bill Cosby, Bill Clinton, and Roger Ailes to name just a few—benefit from the assumption that women are liars. But Thomas and Trump highlight the way in which history repeats itself, even at the highest levels of government.

Men who abuse power should not be given positions of broad public trust. But when women are denied the ability to serve as credible witnesses, it is often impossible to hold men accountable for abuse. A society that won’t listen to women’s warnings is a society that has no defense from those who women warn against. That’s how we got Trump as president.