Moore has vehemently denied the claims, but in an interview with Fox News' Sean Hannity on Friday wouldn't rule out that he had dated girls in their late teens at the time.
Speaking on NBC, Toomey says because the "accusations have more credibility than the denial, I think it would be best if Roy would just step aside".
Moore faces Democrat Doug Jones, 63, a former US attorney, in a special election on December 12 to fill the Senate seat vacated by Jeff Sessions, now the USA attorney general. Kate McKinnon as Jeff Sessions! Moore won the September 26 primary election by about 9 percentage points over odd, who was backed by President Donald Trump. Losing the special election to a Democrat would imperil Republicans' already slim 52-48 majority in the Senate, which is hoping to pass a tax overhaul this year.
A defiant Roy Moore on Saturday insisted the allegations of sexual misconduct decades ago were false and voters in Alabama would "see through this charade". "The president and others in the Republican Party have made clear that if the allegations are true, this man should step aside".
Many Republican lawmakers had already distanced themselves from Moore, who was twice removed as chief justice of the Alabama Supreme Court for defying federal court rulings.
Hope Yen and Kevin Freking are Associated Press writers.