Rep. Katie Hill is the first female member of Congress to resign from office over a sex scandal, a move that several male lawmakers have made throughout U.S. history.

The California Democrat announced her resignation on Sunday amid a House Ethics Committee investigation into her alleged affair with her legislative director, and after news broke that she had also engaged in a three-way relationship with her husband and a campaign staffer.

Hill, 32, denied last week that she ever had an inappropriate relationship with her legislative director Graham Kelly and blamed her "abusive husband" Kenny Heslep for launching a "smear campaign" against her with the rumor. She has, however, admitted to the relationship with the campaign staffer after naked photographs from their relationship were published.

The House Ethics Committee announced on Oct. 23 an investigation into allegations of an affair with Kelly, which is prohibited by House rules, making her the first woman in Congress to face a House Ethics Committee inquiry into a sexual relationship. However, the freshman Democrat will exit her first term before the investigation culminates.

Dozens of members of Congress have been involved in Capitol Hill sex scandals, with many choosing to resign from their positions. While members of both parties have been implicated, those who resigned as a result, to date, have all been men.

In 2007, for example, then-Idaho Sen. Larry Craig stepped down over a sex scandal in which he was arrested in a sex sting in a Minneapolis airport bathroom. The Republican later pleaded guilty to disorderly conduct and announced his resignation.

Former Republican Rep. Chris Lee also resigned from office amid reports that the married lawmaker had sent inappropriate emails to a woman he met on Craigslist, including one with a bare-chested photo of himself, in 2011. Another Republican, former Rep. Mark Foley of Florida, similarly quit when sexually explicit instant messages he had sent teenage congressional pages surfaced in 2006.

More recently, ex-Democratic Sen. Al Franken chose to leave office in 2018 after many of his colleagues urged him to resign amid several allegations of sexual misconduct. The former Minnesota senator has since indicated that he regrets resigning despite facing fresh accusations.

Hill's exit from Congress comes as her fellow Democrats largely remained silent on the issue. Her GOP challengers, meanwhile, had already begun seizing on the scandal.