WASHINGTON — After making the transition from comedy to politics, Senator Al Franken, Democrat of Minnesota, positioned himself as a staunch defender of women’s rights. “Sexual harassment and violence are unacceptable,’’ he wrote on Twitter last month. “We must all do our part to listen, stand with and support survivors.’’

Now it is Mr. Franken who stands accused, and his uncompromising stance in support of “survivors” of harassment has left him few options but to apologize and try to weather the storm. On Monday, a second woman said the senator touched her inappropriately, telling CNN that he grabbed her rear end as her husband took a photo of the two of them at the Minnesota State Fair in 2010. Mr. Franken said that he did not remember the episode but that he was contrite nevertheless.

The disclosure — just days after Leeann Tweeden, a radio news anchor in California, accused Mr. Franken of forcibly kissing and groping her while he was working as a comedian in 2006 — complicates an already tenuous situation for Mr. Franken, making it more difficult for him to carry out his senatorial duties and raising questions about whether his political career can survive as he is likely to face an ethics investigation.

Already, a rape victim with whom he was working on legislation has asked him to no longer sponsor the bill, which called for federal funding to train law enforcement officers in how to interview victims of sexual trauma. The victim, Abby Honold, 22, said in an interview on Monday that she had asked Mr. Franken’s Minnesota colleague, Senator Amy Klobuchar, to take over his work on the measure.