Less than two hours before Mr. Moore released the letter, a lawyer for him, Phillip L. Jauregui, moved to cast doubt on the credibility of Beverly Young Nelson, who accused Mr. Moore of assaulting her in 1977. He suggested that Ms. Nelson, who came forward Monday, had lied when she said she had no contact with Mr. Moore after the alleged assault.

Mr. Jauregui also suggested that a purported message from Mr. Moore to Ms. Nelson in a high school yearbook may have been a forgery, which Mr. Moore’s allies said may have been made using filings related to a divorce case for Ms. Nelson. Mr. Jauregui demanded that Ms. Nelson and her lawyer, Gloria Allred, allow the yearbook to be studied. He did not respond to the substance of Ms. Nelson’s sexual assault allegations, and he did not address the accounts of any other woman who spoke about their encounters with Mr. Moore.

Ms. Allred said that she and her client would release the yearbook if a Senate committee agreed to hold a hearing about the allegations against Mr. Moore.

The pushback by Mr. Moore’s campaign came as a state party committee met on Wednesday afternoon, in Hoover, Ala., near Birmingham, to discuss whether Mr. Moore should remain the Republican nominee for the Dec. 12 special election. The party did not comment on Wednesday night, but Republican activists said they believed officials had contemplated withdrawing the party’s nomination of Mr. Moore.

It was not immediately clear how much the efforts by the Moore campaign and the new accounts would affect the Senate race. Before the new allegations became public, but after women described advances or misconduct from Mr. Moore when they were teenagers and he was in his 30s, Republican officials began distancing themselves, and their party’s money, from his campaign.

Asked at a meeting of Republican governors if she was still backing Mr. Moore, Gov. Kay Ivey of Alabama replied, “The election will be Dec. 12.” (She had said this month that she would vote for Mr. Moore, but would not endorse his candidacy.)