Those allegations have turned the December 12 special election in the reliably Republican Alabama into a close contest between Moore and Democratic nominee Doug Jones. But Moore was already a controversial figure -- beloved by some evangelical Christians in Alabama, but seen as toxic to the Republican brand by national party figures.
While the accusations have placed him in the national political spotlight, the 70-year-old Moore has been engulfed in controversy through much of a two-decade stretch that began when he became Alabama's chief justice in 2001.
Moore is perhaps best known for his strident opposition to LGBT rights and Islam and embrace of Christian theocratic principles.
Here are four things to know about Moore's history of controversy-making actions and remarks:
1. He was ousted as state Supreme Court chief justice -- twice
Moore was more than two years into his first tenure as Alabama chief justice when he was kicked off the state Supreme Court in November 2003.
The reason: He refused to obey federal and state court orders to remove a 5,280-pound stone monument of the Ten Commandments.
After running a foundation and a failed run for governor, Moore launched a campaign for his old job and was elected chief justice again in 2012.
But he was removed again in 2016 after telling probate judges not to follow the US Supreme Court's ruling legalizing same-sex marriage.
The Alabama Court of the Judiciary, a special Alabama court that removed Moore as chief justice, reached the unanimous view that he had not been "credible"
when he denied attempting to contravene a Supreme Court ruling on same-sex marriages.
The court focused on Moore's "misleading" statements. It said Moore's 2016 assertion "that his actions and words mean something other than what they clearly express is not a new strategy."
Moore declared at the time that the complaint against him that led to his ouster was "a politically motivated effort by radical homosexual and transgender groups to remove me as chief justice of the Supreme Court because of outspoken opposition to their immoral agenda."
2. He vehemently opposes LGBT rights
Moore's anti-LGBT stances extend far beyond his opposition to the Supreme Court's ruling.
In 2005, Moore said in a radio interview that "homosexual conduct should be illegal" and that homosexuality is "the same thing" as bestiality.
Moore made similar comments in a 2015 video posted on YouTube by user Lone Star Q. In the video, Moore was asked, "Do you still think that homosexuality should be illegal?"
In 1997, Moore -- then a circuit judge -- was removed from a case after he ruled that a woman who had a lesbian affair couldn't visit her children
unsupervised or with her partner, writing that the "minor children will be detrimentally affected by the present lifestyle" of the mother.
"The court strongly feels that the minor children will be detrimentally affected by the present lifestyle of (Borden) who has engaged in a homosexual relationship during her marriage, forbidden both by the laws of the State of Alabama and the Laws of Nature," Moore wrote in his ruling.
In 2006, Moore called the appointment of an "admitted homosexual" to an ambassadorship an "open affront to Christian principles."
Moore has repeatedly appeared on a radio program hosted by a controversial pastor who has preached the death penalty for homosexuality
More recently, he has made opposition to transgender rights the central talking point of his campaign speeches.
"I oppose transgender rights. There is no right to believe you're a person of the opposite sex or opposite gender," Moore said at a campaign event Monday night.
3. He wants a Christian government
Moore is a staunch evangelical Christian whose calls for a more direct role for Christianity in American society is at the core of his political identity.
Prayers -- both before and after Moore speaks -- are a staple of every campaign event. His support base is made of evangelical Christians.
In a February speech at the Open Door Baptist Church, Moore suggested that the September 11, 2001, terror attacks happened because the United States had distanced itself from God.
"Because you have despised His word and trust in perverseness and oppression, and say thereon ... therefore this iniquity will be to you as a breach ready to fall, swell out in a high wall, whose breaking cometh suddenly at an instance,'" Moore said, quoting Isaiah 30:12-13. Then he added: "Sounds a little bit like the Pentagon, whose breaking came suddenly at an instance, doesn't it?"
Moore continued, "If you think that's coincidence, if you go to verse 25, 'there should be up on every high mountain and upon every hill rivers and streams of water in the day of the great slaughter when the towers will fall.' You know, we've suffered a lot in this country, maybe, just maybe, because we've distanced ourselves from the one that has it within his hands to heal this land."
Later in the same speech, Moore suggested God was upset at the United States because "we legitimize sodomy" and "legitimize abortion."
On the eve of Alabama's Senate Republican primary in September, Moore -- chatting with reporters from CNN, Vox and The Washington Post -- pulled laminated pages from Joseph Story's 1833 "Commentaries on the Constitution" from his briefcase and discussed the government's "duty to foster religion and foster Christianity."
"He said at the time of the adoption of the Constitution that 'it was the general, if not the universal, sentiment in America that Christianity ought to be favored by the state so far as was not incompatible with the private rights of conscience.'"
4. He's taken extreme stances against Islam
It was just one in a long line of anti-Islam comments Moore has made.
In 2006, Moore wrote in an op-ed on the far-right website World Net Daily
that then-Rep.-elect Keith Ellison, a Minnesota Democrat and the first Muslim ever elected to Congress, shouldn't be allowed to take office.
In 2015, Moore's Facebook page shared a Franklin Graham call to stop all Muslims from coming
to the United States.
Moore has offered no indication that his anti-Islam beliefs have changed.
In the September conversation with three reporters on the eve of the primary, Moore falsely claimed that jurisdictions in Illinois and Indiana were being governed with Sharia law.
"There are communities under Sharia law right now in our country. Up in Illinois. Christian communities; I don't know if they may be Muslim communities," Moore said.
Asked which communities are under Sharia law, he said: "Well, there's Sharia law, as I understand it, in Illinois, Indiana -- up there. I don't know."
Pressed again by Vox's Jeff Stein, Moore said: "I was informed that there were. But if they're not, it doesn't matter. Sharia law incorporates Muslim law into the law. That's not what we do. We do not punish people according to the Christian precepts of our faith -- so there's a difference. I'll just say: I don't know if there are. I understand that there are some."
There are no known instances of American laws being codified explicitly according to Sharia principles. Though because Sharia is widely understood to contain prohibitions on acts like theft and murder, it is true that some of its principles are present in many existing American laws.