Karen Kraushaar's identity was revealed by the website The Daily on Tuesday. She is a spokesperson for the Inspector General at the Internal Revenue Service.
Kraushaar told ABC News that she tried to dodge the media spotlight because she feared retaliation from Cain supporters. She has hired a security team to guard her Washington, D.C., home.
Kraushaar is one of four women who accuse Cain of sexual harassment. According to ABC News, Kraushaar left the National Restaurant Association after receiving a reported $45,000.
In a press conference Tuesday, Cain adamantly denied the allegations.
"I have never acted inappropriately with anyone, period," Cain said. "The charges and the accusations I absolutely reject. They simply didn't happen. They simply did not happen."
Kraushaar's complaint was found to be baseless, Cain said, but he did not deny the payment.
Another accuser, Sharon Bialek, held a news conference Monday with attorney Gloria Allred, saying Cain made sexual advances toward her in 1997. She alleged Cain groped her in a car outside the National Restaurant Association.
Cain called Bialek a troubled woman.
"I saw Ms. Allred and her client yesterday in that news conference for the first time. I don't even know who that woman is," Cain said.
Responding to Cain's statement that he has never seen Bialek, she said Cain has "complete amnesia."
"Pathological liars usually do those kinds of things," she said.
Cain says he would be willing to take a lie detector test, but he says he won't submit to one without good reason.
Kraushaar told ABC News that she would be willing to do a joint press conference with Bialek and the other two unidentified accusers.
Bialek said she is grateful that Kraushaar has stepped forward.
A fifth woman, Donna Donella told ABC News that Cain asked her to set him up with a woman after he gave a speech. Donella said he had just finished talking about family and Christian values.
"He came to Egypt, he gave his seminar, and then after he was done speaking, there was a Q and A portion and a woman in the audience asked a question," Donella said. "Shortly after he left the stage, he approached a colleague and myself and said something to the effect of, 'Could you please put me in touch with the lovely young woman in the audience who asked me the question so I can give her a more detailed answer over dinner?'"
The Associated Press contributed to this story.