A second charge of interference with privacy against the 62-year-old senator was dismissed. Mr. Craig was fined more than $500 at the Aug. 8 proceedings and was placed on unsupervised probation for one year. His 10-day jail sentence was suspended, according to a copy of a court document in the case.

According to a police report obtained by Roll Call, the Capitol Hill newspaper that disclosed the episode and guilty plea today, a plainclothes police officer investigating complaints of sexual activity in the bathroom arrested the senator on June 11 after what the officer described as sexual advances made by Mr. Craig from an adjoining stall.

Roll Call reported that the officer said Mr. Craig tapped his foot as a signal to engage in lewd conduct, brushed his foot against the investigator's and waved his hand under the stall divider several times before the officer showed him his badge. After his arrest, the senator denied any sexual intent and in a statement issued this afternoon he attributed the matter to a misunderstanding.

"At the time of this incident, I complained to the police that they were misconstruing my actions," Mr. Craig said in a statement. "I was not involved in any inappropriate conduct.

"I should have had the advice of counsel in resolving this matter. In hindsight, I should not have pled guilty. I was trying to handle this matter myself quickly and expeditiously."

Mr. Craig, whose seat is up for election next year, is the second Republican senator in recent weeks to find his personal behavior under scrutiny. Senator David Vitter of Louisiana was implicated in a separate case in the Washington area when his phone number turned up in the records of an escort service. He made a public apology for what he described as "a very serious sin in my past," but he has not been charged with any crime.

In the Senate, Mr. Craig, who is married and has three children, is known for his advocacy for the rights of gun owners and has a close association with the National Rifle Association. When Republicans controlled the Senate in the last Congress, Mr. Craig was chairman of the Veterans Affairs Committee. He is a former member of the party's Senate leadership. He represented Idaho in the House before first winning election to an open Senate seat in 1990 and he was easily re-elected in 1996 and 2002.

In 2006, Mr. Craig publicly rejected allegations by a gay rights advocate that he had engaged in a homosexual behavior, calling them "completely ridiculous."