"The President believes that these allegations are very troubling and should be taken seriously, and he believes that the people of Alabama should make a decision on who their next senator should be," Sanders said.
The national Republican Party and the campaign arm of Senate Republicans have severed ties with Moore's campaign, and dozens of Senate Republicans have called for Moore to drop out.
The Washington Post published a report
based on interviews with more than 30 people that said Moore pursued relationships with teenage women while he was in his 30s. One woman said she was 14 years old when Moore initiated sexual contact with her.
Since the Post's report, more people have come forward with accusations against the controversial Republican nominee. A woman on Monday accused Moore of sexually assaulting her at age 16.
Moore on Thursday continued to deny the allegations against him as more women have come forward.
"They're not only untrue, but they have no evidence to support them," Moore said in Birmingham, Alabama.
The White House said last week that Trump believes Moore should drop out if the allegations against him are true, but Sanders on Thursday declined to say what mechanism the President believes should be used to determine the truth of the allegations. Sanders suggested "possibly by a court of law."
Sanders said she does not know whether Trump would vote for Moore if he were an Alabama resident.
Trump has been mum on the allegations, ignoring questions about his support for Moore after delivering unrelated remarks at the White House on Wednesday.
Sources close to the White House told CNN
on Wednesday that Trump believes the allegations against Moore are bad for the party's brand, but is reluctant to come out forcefully against Moore because of sexual misconduct allegations he himself has faced. Trump was accused of sexual harassment or sexual assault by a dozen women in the final month of his campaign for president last year.
The White House has mulled different scenarios to possibly thwart Moore from winning election, including a write-in campaign by Attorney General Jeff Sessions or pressuring Alabama's governor to push back the election, but so far no plausible option has emerged.