VIRGINIA LT. GOV. Justin Fairfax has now been accused of sexual assault by two women, neither of whom has any apparent reason to lie. If Mr. Fairfax does not resign, as he has been urged to do by many prominent Virginia’s Democrats and Republicans, the state should undertake an immediate inquiry into the allegations against him. They cannot be allowed to fester.

The furor around Mr. Fairfax, a Democrat and former federal prosecutor, involves allegations of criminality: First, the accusation by Vanessa Tyson, now a college professor, that he forced her to perform oral sex on him nearly 15 years ago in a hotel room in Boston. Second, the accusation by Meredith Watson that he raped her when both of them were undergraduates at Duke University in 2000.

Reporters for The Post looked into Ms. Tyson’s story a year ago and could not corroborate it; nor did they find evidence of similar accusations against Mr. Fairfax. Ms. Watson’s decision Friday to make her allegation public suggests a pattern of conduct by Mr. Fairfax. Each woman’s account appears credible on its face. Taken together, they are a grave indictment — not least because Ms. Watson told a college friend at the time that she had just been attacked by Mr. Fairfax. (She told another classmate the same thing in 2016, by email.) The fact of contemporaneous and past witnesses, who also have no apparent motive to lie, cannot be lightly dismissed.

There may be no ironclad way to determine the truth. However, it is possible to draw conclusions about Mr. Fairfax’s conduct under fire in recent days, and they’re not flattering. Mr. Fairfax has denied both women’s accounts, and in the course of those denials has issued baseless and reckless statements, saying Friday he is the victim of a “vicious and coordinated smear campaign.”

In an attempt to discredit Ms. Tyson’s story, he mischaracterized The Post’s reporting a year ago, then accused the paper of trying to “smear” him when its editors set the record straight. He tried to slime Ms. Tyson by insisting she was “very much into” their sexual encounter. He falsely suggested that her account was somehow discredited by a 2007 video in which she recounted being sexually molested as a child but did not mention the 2004 incident. Without evidence, he also hinted that Virginia Gov. Ralph Northam or Levar Stoney, the mayor of Richmond, could be behind Ms. Tyson’s allegation.

Mr. Fairfax’s conduct is ample reason to believe he lacks the character or temperament to continue in public service.

The scandals in Virginia are inevitably bound up with politics. Democrats worry it may look bad if Mr. Fairfax, who is African American, resigns, while fellow Democrats Mr. Northam and Attorney General Mark R. Herring, who face their own scandals stemming from admissions that they wore blackface as young men, remain in office.

Optics are one thing. Suitability for office is another. Virginians cannot be expected to tolerate a high-ranking official who is credibly accused of rape and sexual assault. That’s why, if Mr. Fairfax defies the calls for his resignation, a full investigation is essential.

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