The Senate Republican campaign arm released a poll showing Roy Moore trailing his Democratic opponent by 12 points.
In the poll, reported by Politico, Democrat Doug Jones leads the former state supreme court judge with 51 percent support compared to 39 percent for Moore.
The survey was conducted Sunday and Monday following allegations of sexual misconduct against Moore, including that he pursued a sexual relationship with a 14-year-old girl when he was in his early 30s.
There have been a growing chorus of Republicans calling on Moore to drop out of the race.
Senate Majority Leader Mitch McConnell (R-Ky.) said the only option appears to be a write-in candidacy for another Republican. Some have floated Attorney General Jeff Sessions, who previously held the seat, but Sessions has said he is not interested.