Republican Senate candidate Roy Moore has denied historical claims he sexually abused a 14-year-old girl in the 1970s.
Leigh Corfman, now 53, told The Washington Post that she was approached by Mr Moore, then a 32-year-old assistant district attorney, outside an Alabama courtroom in 1979.
Days later, it is alleged Mr Moore took the teenager to his house where they engaged in sexual activity before she asked to be taken home.
Representatives for Mr Moore have denied the abuse allegations, describing them as "the very definition of fake news and intentional defamation".
Their statement also noted that Mr Moore – a 70-year-old former state Supreme Court judge – has been married to the same woman for 33 years and has four children and five grandchildren.
In a series of tweets, Mr Moore claimed the allegations were part of a bid to "silence and shut up Christian conservatives like you and me", adding: "I will NEVER GIVE UP the fight!"
He also issued a fundraising appeal asking for emergency donations in a "spiritual battle".
The White House said Donald Trump, who is currently on a tour of Asia, believes a "mere allegation" from many years ago should not be allowed to destroy a person's life.
But press secretary Sarah Huckabee Sanders added: "The President also believes that if these allegations are true, Judge Moore will do the right thing and step aside."
Steve Bannon, Mr Trump's former chief strategist and a vocal supporter of Mr Moore, responded to The Washington Post's report by calling the newspaper part of the "opposition party".
But Republican senator John McCain has called for Mr Moore to "immediately step aside" from the special election due to take place on 12 December, tweeting that the allegations were "deeply disturbing and disqualifying".
Senate majority leader Mitch McConnell added: "If these allegations are true, he must step aside."
In Alabama, the statute of limitations for bringing felony charges involving sexual abuse of a minor in 1979 would have run out three years later.
Ms Corfman never filed a police report or a civil suit, The Washington Post said.
Mr Moore won the right to represent the Republicans in the Senate election after surviving a bruising primary that divided the party, including Mr Trump and Mr Bannon.
The President backed senator Luther Strange in the contest, while Mr Bannon and much of the far-right portion of the party backed Mr Moore.
He was considered a heavy favourite to win the race in deeply Republican Alabama, which is to fill the seat of US attorney general Jeff Sessions.