A second woman came forward Friday with claims that she had been sexually assaulted by Lt. Gov. Justin E. Fairfax of Virginia, intensifying the weeklong political crisis in the state and leading top fellow Democrats to call for Mr. Fairfax to resign.

The woman, Meredith Watson, accused Mr. Fairfax of raping her in 2000 while they were students at Duke University, saying in a statement that his actions were “premeditated and aggressive” and demanding that he step down immediately.

Ms. Watson spoke out two days after Vanessa C. Tyson, a political science professor from California, said she was assaulted by Mr. Fairfax during the 2004 Democratic National Convention in Boston.

By Friday night, Mr. Fairfax was facing a wave of calls for his resignation. Democrats in the Virginia House and Senate urged him to step down, saying he “could no longer fulfill his duties to the commonwealth,” as did the Virginia Legislative Black Caucus, a powerful bloc within the General Assembly. Patrick Hope, a Democrat in the Virginia House, said he would introduce articles of impeachment on Monday if the lieutenant governor had not resigned.

“Everything she said in her statement was exactly what she told me when we talked,” said Diane L. Rosenfeld, a founding director of the Gender Violence Program at Harvard Law School, who said Dr. Tyson told her of the alleged assault in December 2017.

“She’s not doing this for any fame,” Dr. Rosenfeld added. “She’s not suing him for money, so disbelievers and doubters can’t say, ‘Oh, she just wants money.’ She just wants, as she says, the Virginia voters to know who this person is.”

Dr. Tyson has declined to give an interview to The Times. She has said she was spurred to come forward by the realization that Mr. Fairfax might soon become Virginia governor.

In her statement, Dr. Tyson described a forced sexual encounter with Mr. Fairfax in a Boston hotel room while the two were working at the Democratic National Convention in 2004. It began with kissing that was “not unwelcome,” she said, but quickly escalated into non-consensual oral sex.

At the time of the alleged assault, Dr. Tyson was volunteering at a Boston rape crisis center. She had helped start the center’s Survivor Speakers Bureau, where she shared her story about being sexually abused as a child.

In separate interviews Thursday and Friday, five friends of Dr. Tyson said she told them of the encounter either in late 2017, early 2018 or last fall. On Friday, after The Times published its article on Dr. Tyson’s supporters, a sixth woman came forward to say Dr. Tyson had also confided in her. Susan J. McWilliams, a politics professor at Pomona College in California, said that in a conversation around the time of Mr. Fairfax’s election as lieutenant governor in 2017, Dr. Tyson told her that he had assaulted her during the 2004 convention.

“I did not know who Justin Fairfax was,” Dr. McWilliams said. “And I immediately went home and Googled him.”

The Stanford fellowship that Ms. Tyson began last fall is merely her latest academic accomplishment after a working-class upbringing in the Los Angeles area, the biracial daughter of a single white mother. Dr. Tyson graduated from Princeton in 1998 and would later tell The Princeton Alumni Weekly that she identified as African-American partly because that was the way the world saw her. “I am biracial, but I could not pass for white,” she said.

She would go on to obtain a masters and doctorate, both in political science, at the University of Chicago.

In a statement issued Thursday, Scripps College in California, where Dr. Tyson is a professor of politics, confirmed that Dr. Tyson “shared with several members of the Scripps community the details about a 2004 sexual assault,” and that those conversations “are consistent” with her written account.

Friends describe Dr. Tyson as gregarious, and a mentor to younger scholars, particularly people of color. “Academics are socially awkward people,” Dr. Brown said. “We tend to be a lot more introspective and quiet and reserved, and she pulls people out of their shells.”

Dr. Freyd, the Oregon professor who is also doing a fellowship at Stanford, said that she and Dr. Tyson have become close despite having known each other for only a few months. On Thursday, Dr. Freyd joined 35 other fellows at Stanford’s Center for Advanced Study in the Behavioral Sciences to support her.

Next Tuesday, Drs. Tyson and Freyd are planning a symposium at Stanford — arranged well before Dr. Tyson disclosed her allegations. It is titled “Betrayal and Courage in the Age of #MeToo.”