Roy Moore will face an investigation by the Senate Ethics Committee if he wins the special election for the U.S. Senate seat on Dec. 12, Senate Majority Leader Mitch McConnell warned on Tuesday.

The Wall Street Journal reported that McConnell said the Republican candidate would be asked to testify under oath during the investigation. Other Republican senators have supported the idea of voting to expel Moore if he wins.

McConnell's warning comes nearly a week after the Washington Post published an article accusing Moore of pursuing four teens while he was in his 30s during the 1970s. On Monday, a fifth woman came forward accusing Moore of sexual assault. The fifth woman said she was 16 years old and he was 30 during the incident in December 1977.

"It would be a rather unusual beginning," McConnell told The Wall Street Journal at a CEO Council event on Tuesday. "I'd like to save the seat, and it's a heck of a dilemma when you've got a completely unacceptable candidate bearing the label of your party within a month of the election."

Moore denies any wrongdoing and believes the allegations are part of an attack on his campaign.

The deadline to take Moore's name off the ballot passed in mid-October. If Moore is elected, there can be a vote to expel him from the senate, which would require a two-thirds margin. Then Gov. Kay Ivey could appoint a temporary replacement.

McConnell also proposes Attorney General Jeff Sessions as a write-in candidate.

"He's totally well known and extremely popular in Alabama," McConnell said.