In the dizzying hours since the yearbook photo surfaced on Friday, Mr. Fairfax, who would be the state’s second black governor, has treaded cautiously in the public eye.

Mr. Northam, who at first apologized for the yearbook photo, changed course on Saturday in a strange, lengthy news conference, insisting that he was not either of the people depicted. But even as Mr. Northam resisted calls to resign, he acknowledged having once applied shoe polish to his face to imitate Michael Jackson in a dance contest.

After the governor spoke, Mr. Fairfax issued a statement saying that Mr. Northam’s actions “at the very least” indicated “a comfort with Virginia’s darker history of white supremacy, racial stereotyping and intimidation.”

“At this critical and defining moment in the history of Virginia and this nation, we need leaders with the ability to unite and help us rise to the better angels of our nature,” Mr. Fairfax said in the statement, which did not call for Mr. Northam’s resignation. A spokeswoman for the lieutenant governor did not respond to a request to interview him.

Mr. Fairfax, a married father of two, grew up in Washington, D.C., in a neighborhood that he described on his campaign website as having shifted “from a close-knit middle-class community to one ravaged by a growing drug epidemic, increasing violence, and dwindling economic opportunities.” He attended Duke University on a scholarship, graduated with a degree in public policy and got a low-level job on Al Gore’s 2000 presidential campaign, compiling briefing books for Mr. Gore’s wife, Tipper.

“There was just sort of a dynamism and kind of an ebullience to him,” said Bruce Jentleson, a Duke professor who worked in the State Department during Bill Clinton’s presidency and who helped Mr. Fairfax get the job on the Gore campaign.

From there, Mr. Fairfax’s career moved fast. He graduated in 2005 from Columbia Law School, where he worked on the Law Review, and served as an intern and clerk for a federal judge in Virginia, Gerald Bruce Lee.