"The President's position hasn't changed. He still finds those concerning," Sanders said of the allegations. "But as we've also said, the President feels that he would rather have a person that supports his agenda versus somebody who opposes his agenda every step of the way."
Sanders' explanation came a day after Trump officially lent his full backing to the Alabama Republican and echoed Trump's own explanation for his endorsement of Moore that came just a week before the special election is set to take place.
"We need (Moore's) vote on stopping crime, illegal immigration, Border Wall, Military, Pro Life, V.A., Judges 2nd Amendment and more," Trump tweeted.
Moore has been accused of initiating sexual contact with a 14-year-old girl, sexually assaulting a 16-year-old and pursuing relationships with teenage girls, all when he was in his 30s. Moore has denied all the allegations.
The endorsement was the culmination of several weeks during which the President moved from expressing guarded concern over the allegations to fully endorsing Moore after first emphasizing Moore's emphatic denials of the allegations.
Trump's position on Moore went against the grain of most prominent Republicans in Washington, including Senate Majority Mitch McConnell, who initially called on Moore to drop out.
But Sanders insisted Tuesday that despite his endorsement, Trump still stands by his initial statement: that Moore should "step aside" if the allegations are true.
"But we don't have a way to validate that. And that's something for the people of Alabama to decide," she added.
Trump's belief that the allegations are "concerning" and "troubling," as Sanders once again said Tuesday, has only been expressed through Sanders. In his own public comments on the matter, Trump has instead chosen to emphasize Moore's denials and the damage he believes Moore's opponent would do if he is elected.
The latest explanation of Trump's endorsement on Tuesday came hours before the President's former chief strategist Steve Bannon is set to campaign with Moore in Alabama.
Trump is also slated to hold a political rally in Pensacola, Florida, on Friday, where news coverage extends into Alabama. The Trump campaign has also advertised the rally with Trump supporters in Alabama.