Trump noted that Moore, who has been disowned by the leadership of his own Republican Party, disputed all the allegations against him.
"He totally denies it," Trump told reporters before leaving for his Thanksgiving break in Florida, putting himself at odds with almost all of the senior leaders of his party by siding with Moore.
"He says it didn't happen. You have to listen to him also," Trump said.
A GOP source close to the White House told CNN's Jim Acosta that Trump had doubted the accusers alleging misconduct against Moore. The source said Trump sees what's happening to Moore as similar to the accusations of sexual abuse leveled against Trump himself during the 2016 campaign.
Once Trump raised Moore's denials of claims by several women that he sought relationships with them as teens decades ago, he created space for himself to maneuver out of a tough spot and create political advantage.
The President knows that Moore would be a potentially solid vote for Trump-style populism in the Senate, and a thorn in the side of his own establishment foes, as crucial moments loom for the White House agenda.
"We don't need a liberal person in there, a Democrat," Trump said of Moore's opponent in the December 12 election, Doug Jones.
"I've looked at his record. It's terrible on crime. It's terrible on the border. It's terrible on the military ... we do not need somebody that's going to be bad on crime, bad on borders, bad with the military, bad for the Second Amendment," he said.
By reshaping the controversy hammering Moore, Trump also gets to side with his supporters behind a candidate who claims he is the target of unfair vendettas by the media and political establishment and who is backed by his former political guru, Steve Bannon.
And he can showcase his own willingness to avoid the politically correct course, a tendency that has been an important driver of his success.
Trump's presidency has pulsated with jaw-dropping moments. But the spectacle of the President of the United States effectively endorsing an ally accused of child molestation ranks among the most stunning.
But his decision to take Moore's denials at face value for his own convenience is far from the only occasion when he has taken solace in a preferred version of the truth to satisfy his political requirements.
While he cast doubt on the allegations against Moore, Trump has been willing to believe women who made accusations of assault against men who offer him a juicy political target, for instance former President Bill Clinton and Hollywood mogul Harvey Weinstein.
Just this month, during his Asia tour, Trump turned a similar trick when he cited Russian President Vladimir Putin's denials of election hacking. As with the Moore drama, Trump had decided to believe adamant denials of wrongdoing -- even though most other political leaders believe they are false.
"Every time he sees me, he says, 'I didn't do that.' And I really believe that when he tells me that," Trump told reporters on Air Force One en route to Hanoi on November 11.
His comments caused a furor back in the United States, but allowed Trump to occupy a political safe space and advance his position that the Russian intelligence operation to boost his candidacy -- identified by US spy agencies -- was nothing but a hoax.
Trump later modified his stance, saying that he believes spy agency assessments about election hacking now his appointees are in charge. But his apparent intent, blurring the question of Russia's influence on the election, in an operation meant to help him win, had already been accomplished.
Trump's tendency to chose the most politically advantageous version of reality started as soon as he entered the White House.
He inflated the size of his inaugural crowds, he erroneously called the United States the most taxed nation in the world and claimed he would have won the popular vote in last year's election were it not for "millions" of illegal voters.
His effective endorsement of Moore on Tuesday may well offer a tangible political gain for the President if he wins in Alabama. And it certainly bolstered the firebrand judge's campaign, a factor his aides quickly recognized.
"I think what the President said is that Roy Moore's character, consistent denials, and now the refutation of these stories makes it very clear that the world should consider that these allegations are false," said senior campaign adviser Brett Doster.
Potential political costs
But retreating into his own version of political reality does bring clear political costs.
Most obviously, should Moore actually lose the Alabama race, Trump will have stuck his neck out for no reason.
His decision to embrace Moore also throws another wrench into his rocky relationship with Senate Majority Leader Mitch McConnell, who has said he believes Moore's accusers. It further distances him from the wider Republican establishment. Colorado Sen. Cory Gardner, who chairs the National Republican Senatorial Committee, had said the Senate should expel Moore if he wins.
The saga could also inflict more significant damage to the GOP, and its standing among women voters in future elections -- a problem that was evident in turnout among college educated white women in a gubernatorial election in Virginia this month.
In a wider sense, Trump's defense of Moore also isolates him on the reactionary side of an watershed in social history -- as women who make allegations against powerful men are being believed more widely than they have been in the past -- even when their claims have not been proven in a court of law.
Still, Trump rarely seems to think in terms of history and how he will be viewed in years hence, improvising short-term political decisions in preference to longer-term political plays.
Some Trump critics also believe there is another motive for Trump's decision -- an understanding that he could hardly condemn Moore for denying allegations of sexual impropriety while maintaining his own vigorous attacks on women who accused him of sexual harassment during the 2016 election campaign.
"Trump is a sympathizer for men like Roy Moore because he has his own issues," said CNN legal commentator Areva Martin. "He is never going to come out and attack Roy Moore because there were 16 women who have accused him."
Trump has vigorously denied accusations of sexual harassment and branded all his accusers as "liars."