A former employee of the National Restaurant Association’s educational foundation accused presidential contender Herman Cain on Monday of making an aggressive sexual advance 14 years ago, for the first time putting a name and face with claims of harassment that have plagued Cain for more than a week.

The accusations from Sharon Bialek, a single mother from Chicago, threw Cain’s campaign into another day of turmoil when she described how he allegedly sexually harassed and groped her while the two sat in a car together in Washington. At the time of the alleged incident, Bialek said, she had recently lost her job at the restaurant association, where Cain was chief executive, and was seeking his help finding work.

When she told him to stop touching her, she said, Cain replied: “You want a job, right?”

“I was very surprised and shocked,” Bialek said, choking up as she spoke to reporters at a news conference in Manhattan. “I said, ‘What are you doing? You know, I have a boyfriend. This isn’t what I came here for.’  ”

Cain’s campaign quickly issued a statement denying “all allegations of harassment” and accused Bialek’s lawyer, Gloria Allred, of “bringing forth more false accusations” against the Republican candidate. The campaign said Cain would hold a news conference Tuesday afternoon in Phoenix to address the allegations.

Cain went on ABC’s “Jimmy Kimmel Live” Monday night and vowed to fight the claims head on. “There is not an ouce of truth to all these allegations,” he said.

The statement from his campaign said Bialek had been “convinced” to come forward by Cain’s opponents, and described Bialek as “a woman with a long history of severe financial difficulties, including personal bankruptcy.”

Bialek said in television interviews on Tuesday that she was acting entirely on her own, and was not being paid for speaking out.

The stark details of her account added a new dimension to a scandal that has dominated the news since Politico first broke the story on Oct. 30. Her allegations moved the controversy beyond the realm of misunderstandings or jokes that several Cain operatives have suggested are at the root of other harassment claims. Bialek said Cain forcefully touched her, putting his hand up her skirt, reaching for her genitals and pushing her head down toward his crotch.

Allred said that Bialek had come forward not for personal gain but to give a “voice” to the other women who alleged harassment, and that Bialek had chosen not to sell her story or file a lawsuit. Bialek had told two people — a former boyfriend and a businessman in Chicago — her story at the time of the alleged incident, Allred said. She held up two pages that she said were sworn affidavits from the two men supporting Bialek’s account.

Bialek was born and raised in Chicago and has lived there most of her life, according to Allred. She is a Republican, a stay-at-home mother of a 13-year-old son, and a college graduate who has worked as host of a cooking show, an account manager at Revlon and a director of corporate development at the Easter Seal Society, Allred said.

Three other women have alleged that Cain harassed them at the National Restaurant Association, which he led from 1996 to 1999. He had previously served as CEO of Godfather’s Pizza. The association reached settlements with two of the women, providing a payment for each when they left their jobs. In at least one instance, Cain was not a party to the agreement and admitted no guilt, according to the organization.

A third woman told the Associated Press last week that she also was harassed but did not file a complaint.

Joel P. Bennett, an attorney for one of the women, released a statement from his client Friday claiming she was harassed over a span of months. He said Monday that Bialek’s account is remarkably similar to his client’s experiences, although he would not elaborate.

“I consider it corroborating evidence,” Bennett said.

He said he believes Bialek called his office last week and left a message saying she wanted to go public. When he returned her call the next day, she had changed her mind.

“Our client is very brave to have come forward,” Allred said. “She knows that stepping out into the light, she will face public scrutiny.”

It is unclear whether Bialek’s account will hurt Cain’s popularity among Republican voters. A new Washington Post-ABC News poll released Friday showed that Cain’s status alongside former Massachusetts governor Mitt Romney at the front of the Republican field was intact.

Debra S. Katz, a Washington lawyer specializing in workplace discrimination, said the behavior described by Bialek is “coercive and physical” and cannot be explained away as a misinterpretation. “This is abuse of power. This is sexual battery.”

Public records of Bialek’s personal financial circumstances show a woman who has been intermittently in financial straits. She has filed for bankruptcy twice, in 1991 and 2001, and she has an Internal Revenue Service tax lien of $5,176. When asked at the news conference, Allred said Bialek is not on public assistance.

A man who identified himself as her fiance, Mark Harwood, told WBBN radio in Chicago, “My heart of hearts says the reason she’s come forward is to be the voice of these other ladies . . . vindicate herself a little bit.”

Bialek’s father, Chester “Henry” Bialek, 86, described his youngest daughter as politically conservative and an “outgoing person, kind and considerate.”

“She is involved in PTA and drives her son to his football games,” Chester Bialek said in an interview with The Washington Post. “She’s independent. She’s had some bad luck, but she overcame adversity, mostly in the romance angle. Just unfortunate relationships, but otherwise everything is okay.”

At the news conference, Bialek emphasized that it was her then-boyfriend who had urged her in 1997 to seek Cain’s help in finding work after losing her job at the National Restaurant Association’s educational foundation in Chicago, where she had worked for about six months. She had met Cain three or four times and, about a month before losing her job, she and her boyfriend had sat next to him at a hospitality industry event. She said she had found his speeches “inspiring” and had asked him when he was going to run for president.

In July of that year, she called Cain, who agreed to meet her in Washington during a trip she was making to visit family on the East Coast. She said her boyfriend booked her a room at the Washington Hilton, and Cain suggested they meet at the hotel bar.

When Bialek checked into the hotel, she found she had been given a “palatial” suite and assumed her boyfriend was responsible. But when she met Cain in the lobby, he asked her how she liked her room. “Mr. Cain kind of smirked and said, ‘I upgraded you,’ ” she said.

He became aggressive in the car after they went out to dinner, she said.

Bialek said she saw Cain again about a month ago at a tea party conference in Chicago. She approached him, she said, and asked, “Do you remember me?”

“I guess I wanted to see if he was going to be man enough to own up to what he had done some 14 years ago,” she said. “He acknowledged that he remembered me from the foundation, but he kind of looked uncomfortable. And he said nothing as he was whisked away for his speech by his handlers.

“I really didn’t want to be here today and would not have been here were it not for the other women who have alleged sexual harassment,” Bialek said at the end of her remarks Monday. She then addressed Cain directly: “Just admit what you did. Admit you were inappropriate to people. And then move forward.”

Staff writers Colum Lynch, James V. Grimaldi, Karen Tumulty and Nia-Malika Henderson; staff researcher Lucy Shackelford; and research editor Alice Crites contributed to this report.