Despite a sexual harassment scandal involving its best-known personality, Bill O’Reilly, Fox News insisted last week that neither the star host nor his highly rated show, “The O’Reilly Factor,” has been tarnished. So far commercial sponsors are sticking with the show, according to a spokeswoman for Fox News. “We haven’t lost any advertisers,” she said.

The stakes are large for Fox and Mr. O’Reilly, who is also a best-selling author, newspaper columnist and daily radio talk show host. “The O’Reilly Factor” is the most-watched brand in cable news, bringing in about $60 million a year for Rupert Murdoch’s media empire. Mr. O’Reilly’s newspaper syndicate said in a statement it is backing him up and still distributing his column to 300 newspapers.

“What I think agencies will do is evaluate public opinion,” said Peter Olson, executive VP of national buying at Mediacom. “If it goes the wrong way for O’Reilly, we have to consider what to do.”

Another senior agency executive, who asked not to be named, said he sent out a memo asking buyers at his agency to re-evaluate purchasing spots on “The O’Reilly Factor.” He added that he had not “had any clients call me and say ‘Get out of the Bill O’Reilly show,'” but he planned to tell clients about the controversy and ask whether, in light of this, they still wanted to have their products on the show. In the case of Martha Stewart, he noted, “clients did not pull out until she was convicted.”

Richard Hanley, a professor of journalism at Quinnipiac University in Connecticut and a frequent guest on “The O’Reilly Factor,” said the current situation for Mr. O’Reilly was “uncharted territory. Until the case winds its way through the system, until the allegations are proven or disproven, we can’t prejudge. There will be a lot of spin back and forth.”

The charges come at an awkward time for Fox News, which is riding high at the top of the cable news ratings heap, and only a few weeks ahead of a presidential election. Mr. O’Reilly is expected to be a prominent part of that coverage on election night.

The controversy became public last Wednesday when Mr. O’Reilly filed a suit against Andrea Mackris, a 33-year-old female TV producer for Fox and before that CNN, charging that he was being blackmailed. A day later Ms. Mackris filed a suit against him alleging sexual harassment, including unwanted attempts at phone sex.

The day after the suits were reported, Mr. O’Reilly appeared on “Live with Regis and Kelly” and accused Ms. Mackris of demanding a $60 million settlement to avoid a lawsuit. “I knew I would perhaps ruin my career” by filing his own lawsuit against Ms. Mackris, he said, adding that he felt compelled to do so because of her settlement demands. “If I have to go down, I’m willing to do it,” he added.

“They want $60 million,” the 55-year-old Mr. O’Reilly, who is married, lamented to the show’s hosts. “Think about it. The 9/11 families are nowhere near that. I just said, ‘Enough, enough,'” apparently referring to settlements the government paid out to the families of 9/11 victims.

In her lawsuit, Ms. Mackris’ attorneys state that Fox News makes $60 million a year from “The O’Reilly Factor.” The lawsuit filed on behalf of Fox News calls the alleged demand “blackmail, pure and simple,” and “an extortion scheme.” The Fox suit alleges that prior to Sept. 29, Ms. Mackris had not complained to “anyone in authority” about Mr. O’Reilly.

Asked for comment, a spokeswoman for Fox News said, “It’s all out there” in the lawsuit that Fox’s attorneys filed against Ms. Mackris and her attorney, Benedict Morelli. Neither Mr. Morelli nor Fox law firm Epstein, Becker & Green had any other immediate comment.

Both lawsuits were posted on The Smoking Gun Web site last week, and the New York media world was transfixed by the details, which include long, steamy, verbatim quotes from various dinners, which apparently were recorded by Ms. Mackris. The lawsuit alleges that Mr. O’Reilly repeatedly engaged in inappropriate remarks and tried to solicit Ms. Mackris for phone sex and more. Ms. Mackris’ suit alleges that Mr. O’Reilly violated New York State Human Rights Law, Executive Law Section 290.

The Fox spokesperson confirmed that Fox News does have an Equal Employment Opportunity and Unlawful Harassment section in its Standards of Business Conduct. It was unclear last week what might happen to Mr. O’Reilly if any possible tapes reveal that he violated that policy.

Beyond sexual harassment, Mr. O’Reilly is also quoted in the Mackris lawsuit as making bizarre threats against Air America radio talk show host Al Franken, whose most recent book levels many accusations against Mr. O’Reilly.

The suit alleges that Mr. O’Reilly, explaining to Ms. Mackris why no woman would ever surface with sexual harassment complaints, asserted that Fox News CEO Roger Ailes “makes things happen,” and added, “Look at Al Franken, one day he’s going to get a knock on his door and life as he’s known it will change forever.”