The hashtag was unleashed by an analysis of what would happen if only men voted.
The already ugly election cycle took an even darker turn on Tuesday and Wednesday when the hashtag #repealthe19th—an apparent reference to removing women’s right to vote—popped up online.
It sprang up after FiveThirtyEight’s Nate Silver tweeted a gif of what the electoral map would look like if only men voted.
A few Twitter users, voicing their support for Trump, latched onto this idea and added the #repealthe19th hashtag to comments like “men should never have given women the right to vote.” One user, who voiced support for Trump and used the hashtag, said she’d give up her right to vote in order to make the map—and a Trump victory—real. Donald Trump’s son Eric also used the map as an illustration of his father’s “momentum” across the country. He included it in a fundraising email to supporters on Wednesday. “As one of the most dedicated grassroots leaders in the country you know, momentum matters,” the email said. “And right now all the momentum is on our side.” He did not reference the hashtag.
Subscribe to The World’s Most Powerful Women, Fortune’s daily must-read for global businesswomen.
The email prompted immediate backlash from Hillary Clinton supporters who then co-opted the #repealthe19th hashtag and used it to accuse Trump supporters of sexism and misogyny and to motivate their base.
Kamala Harris, the attorney general for California who’s running for the Senate, weighed in, used the hashtag as evidence of bigotry.
New York Senator Kirsten Gillibrand cited it as a reason to register to vote.
Star Trek actor George Takei, who’s outspoken on equal rights, also expressed his dismay at the use of the hashtag.
The hashtag gained traction as Trump became embroiled in more allegations of misconduct toward women. An article The New York Times published Wednesday night cited two women who claim the real estate mogul touched them inappropriately in the past, and a first-person essay by a People writer waged similar allegations. Trump denied all the accusations and his lawyer requested that the Times remove its article. The paper declined.
The Trump campaign did not immediately return a request for comment on the use of the hashtag and on the Eric Trump email that included the image of an electoral map in which only men vote. Fortune will update this post if we hear back.