WASHINGTON — Senate Republicans scrambled on Friday to find a way to block Roy S. Moore’s path to the Senate, exploring extraordinary measures to rid themselves of their own nominee in Alabama after accusations emerged that he had made sexual advances on four teenage girls when he was in his 30s.

Mr. Moore, meanwhile, remained defiant, insisting in a radio interview with Sean Hannity that he would stay in the race. He told Mr. Hannity, the Fox News host, who has endorsed Mr. Moore’s candidacy, that he “never had any contact” with Leigh Corfman, the woman who told The Washington Post that Mr. Moore touched her sexually when she was 14, though he did not deny dating some teenagers.

“I have never known this woman, or anything,” said Mr. Moore, who described the accusations as “politically motivated.”

Republican senators and their advisers, in a flurry of phone calls, emails and text messages, discussed fielding a write-in candidate, pushing Alabama’s governor to delay the Dec. 12 special election or even not seating Mr. Moore at all should he be elected. In an interview, Senator Mitch McConnell of Kentucky, the majority leader, declined to say whether he would agree to seat Mr. Moore should he win. Mr. McConnell deferred a question about a possible write-in campaign by Senator Luther Strange, the current occupant of the seat, to Mr. Strange.