Three months before Representative Anthony D. Weiner sent a photo from his Twitter account to a 21-year-old Washington State college student named Gennette Cordova, a small group of determined, self-described conservatives were warning young women on Twitter, including Ms. Cordova, to be wary of him.
Calling themselves the #bornfreecrew on Twitter, members of the group closely monitored those whom Mr. Weiner was following, taking it upon themselves to contact young women they believed to be “schoolgirls,” and urging them publicly to stay away from him, according to an analysis of posts on Twitter’s public stream.
By early May, members of the group were also speculating that Mr. Weiner would be caught in a sex scandal. The leader, a man who identified himself on Twitter as Dan Wolfe and used the handle @PatriotUSA76, is the same Twitter user who discovered the photograph that Mr. Weiner took of himself and sent to Ms. Cordova. He shared it with his followers and the conservative blogger Andrew Breitbart, who made it public the next day.
As Democrats and Republicans embrace Twitter and other social media tools as a way to interact with their constituents and woo voters, many have discovered a downside to online communication: cyberstalkers, who track and criticize their every move.
But even by the standards of modern politics, Dan Wolfe and other members of the #bornfreecrew watched Mr. Weiner’s account with particular ferocity, and a sharp focus on his interactions with women. In several instances the congressman dropped his online contact with women after they were identified by the crew, suggesting that Mr. Weiner might have been aware of its actions.
There were at least two female high school students among the 191 people Mr. Weiner followed. There is no evidence that he engaged in private discussions with them, and he has said that to his knowledge he has not had any online sexual communications with under-age women.
Mr. Wolfe, whose account vanished from Twitter last Friday, has been one of the more mysterious characters in the congressman’s saga, refusing to reveal his real name even to the other members of the #bornfreecrew. He joined Twitter on Jan. 6 and began posting multiple messages criticizing both Mr. Weiner and his wife, Huma Abedin, a top aide to Secretary of State Hillary Rodham Clinton.
By March, Mr. Wolfe had more than 1,000 followers and was actively befriending fellow conservatives. Group members joined him in scrutinizing those whom Mr. Weiner was following and their Twitter profiles, and commenting if the person he followed was a young woman.
On April 14, for example, Mr. Wolfe tweeted, “Weiner’s new follow is a high school girl. LMAO! Freak!”
Michael Stack, 39, of New Jersey, who describes himself on his Twitter profile as a “Republican who believes in the principles that made this country great,” said he befriended Mr. Wolfe on Twitter (they never met in person or spoke on the phone). “Soon, Dan told me Weiner was following a bunch of girls,” Mr. Stack said. “I thought it was kind of weird.”
Mr. Stack said that Mr. Wolfe had told him in a private message that Mr. Weiner had been following a porn star who was later identified as Ginger Lee. “He tweeted about it and then the porn star was gone,” Mr. Stack said. “He was paying attention,” he said, referring to Mr. Weiner.
On May 5, Mr. Wolfe told him that he had a friend who knew Matt Drudge who had said that a scandal involving a member of Congress was coming soon. The same day that Meagan Broussard, 26, of Texas, said that she had received an e-mail from Mr. Weiner with a photo she had asked him to take, while holding up a white piece of paper that said “me.”
At 6:35 p.m., Mr. Stack, using his Twitter handle, @goatsred, posted: “Rumor … a ‘bigtime’ Congressman caught with mistress. There are pix and a top 5 right-wing blogger has them. @RepWeiner is it you?”
Throughout May, Mr. Wolfe and other members contacted other young women Mr. Weiner was following, including a 16-year-old from California who started a campaign on Twitter to get the congressman to be her prom date.
The next day, Mr. Stack, posting on Twitter, sent her a message saying in part, “if you’re a minor and he’s following you, well, seems a little creepy if not in ny,” copying @RepWeiner on the post. The next day, on May 18, the girl posted: “Well @RepWeiner unfollowed me.”
Michael Madden, 52, a retired Philadelphia firefighter and member of the group, said he had joined Mr. Wolfe in warning young women about Mr. Weiner.
“It seems now that Dan may have had an agenda all along,” he said. “We don’t know yet what it is. But he never said to me, ‘I’m going to get this guy.’ What he said is that it was not right.”