Rep. Katie Hill, D-Calif., says she plans to resign in the face of an ethics investigation stemming from allegations that she had an inappropriate sexual relationship with a member of her congressional staff.

"It is with a broken heart that today I announce my resignation from Congress," Hill wrote in a statement released on Sunday. "This is the hardest thing I have ever had to do, but I believe it is the best thing for my constituents and our country."

Hill, a freshman lawmaker, had been considered a rising star in the Democratic Party. But on Wednesday, the House Ethics Committee announced that it was opening an investigation into allegations that Hill was romantically involved with Graham Kelly, her legislative director. Hill has denied the allegation.

The allegations against Hill were first reported by the the conservative website Red State.In her statement, Hill said she was the victim of a "smear campaign" by her husband — with whom she's engaged in a rancorous divorce proceeding — and "hateful political operatives."

The ethics investigation against Hill was triggered by a change to House rules passed during the height of the #MeToo era. Over the course of six months between 2017 and 2018, nine lawmakers — eight men and one woman — stepped down over varying degrees of sexual misconduct allegations.

One part of the rule change, approved in February 2018, bars lawmakers from engaging in sexual relations with anyone who works in their congressional office or on any committees on which they serve.

With the launch of the ethics inquiry, Hill became the first member of Congress to face investigation for a possible violation of the rule.

Hill, who is openly bisexual, has admitted to and apologized for an "inappropriate" relationship with a female campaign staffer. However, there are no laws or House rules that prohibit consensual relationships with campaign staffers.

Hill did not say when specifically she planned to resign.

In a statement, House Speaker Nancy Pelosi, D-Calif, said that Hill's "errors in judgment" made it "untenable" for her to remain in office. "We must ensure a climate of integrity and dignity in the Congress, and in all workplaces," Pelosi said.

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