Congresswoman blames estranged husband and ‘hateful political operatives’ for smear campaign against her. Who is Katie Hill?
In her resignation letter on Sunday, Ms Hill said stepping down from Congress was the "hardest thing" she had ever had to do.
"Having private photos of personal moments weaponized against me has been an appalling invasion of my privacy. It's also illegal, and we are currently pursuing all of our available legal options," she wrote.
"However, I know that as long as I am in Congress, we'll live fearful of what might come next and how much it will hurt."
Ms Hill has accused her husband, whom she is in the process of divorcing, of trying to humiliate her. She says the campaign relationship began in the final "tumultuous" years of her marriage.
"I know that even a consensual relationship with a subordinate is inappropriate, but I still allowed it to happen despite my better judgment," she said in the letter to supporters. "For that I apologise."
Two years ago during her congressional campaign, she described Kenny Heslep, whom she wed in 2010, in a social media post as "my best friend and the love of my life".
In the statement on Sunday, she defined herself as a "fighter".
"Now, my fight is going to be to defeat this type of exploitation that so many women are victims to and which will keep countless women and girls from running for office or entering public light."
Ms Hill has represented the 25th district in southern California since 2018, when she was elected as part of a Democratic wave.
She is also vice-chairwoman of the House Oversight and Reform Committee, which has been investigating President Donald Trump's financial dealings.
She previously worked as executive director of non-profit organisation People Assisting the Homeless.
California congresswoman Katie Hill, a freshman Democrat and a rising star in the party, announced her resignation on Sunday amid allegations that she had a sexual relationship with a member of her congressional staff.
“It is with a broken heart that today I announce my resignation from Congress,” Hill, 32, wrote in a resignation letter. “This is the hardest thing I have ever had to do, but I believe it is the best thing for my constituents, my community, and our country.”
Last week the House ethics committee opened an investigation into allegations that Hill had engaged in a sexual relationship with her legislative director, Graham Kelly, in possible violation of a House rule forged in response to the #MeToo era. Hill denied the claim in a letter to constituents but admitted to a relationship with a different, unnamed staffer on her congressional campaign that she called “inappropriate”.
House rules enacted at the height of the #MeToo movement in 2018 prohibit relationships between members of Congress and their employees. But the rules do not cover campaign aides.