But Monday, in a teary news conference in New York City, Weiner, 46, 'fessed up. He said he had lied repeatedly out of embarrassment and shame. He had indeed sent the photo to the woman in Washington state, and he also had inappropriate online contact with several others over the last three years.
"I did a regrettable thing, and for that I apologize," Weiner said. "I believe what I did demonstrates a deep personal failing."
Weiner, who has long been expected to run for mayor of New York in 2013, said he would not resign, but would let his constituents decide his fate. It was not immediately clear whether congressional Democrats would react as harshly as Republicans did in February when faced with a similar scandal. They pressed New York Rep. Chris Lee to step down after the married congressman sent a cellphone photograph of himself shirtless to a woman he met on Craigslist.
So far, no Democrats have publicly urged Weiner to resign. But House Democratic Leader Nancy Pelosi of San Francisco and other party officials called for an Ethics Committee investigation to determine whether any official resources were used or any other violation of House rules occurred. Weiner, who told reporters that Pelosi had urged him in a phone call to tell the truth and expressed her disappointment in him, said later he welcomed the investigation.
Before Weiner appeared, Andrew Breitbart, whose conservative news websites had broken the story about Weiner's sexually charged tweets, crashed the news conference. Angry that Weiner's supporters had accused him of hacking the congressman's account, Breitbart took over the hotel microphone for about six minutes.
"Quite frankly, I'd like an apology for him being complicit in a blame-the-messenger strategy," Breitbart said. "So I'm here for some vindication."
The surreal theatrics combined familiar elements of contemporary sex scandals with some newfangled twists -- a partisan Internet entrepreneur with the goods on a wayward politician who tarnished himself using new technology, a teary confession from the hangdog pol, shouted questions from the gathered journalists. And all of it unfurling in real time -- streamed live on the Internet, tweeted by observers or beamed into living rooms on TV.
"This isn't even Shakespearean," said Baruch College professor Doug Muzzio. "It's theater of the absurd. The rule in politics when you do something wrong or stupid is get it out, get it out early because at least you get some credit for getting it out. He kept the story alive, and then after he bleeds for a week, then he decides to come clean. Really bad."
Breitbart, whose site on Monday had posted a photo of Weiner bare-chested obtained from a second woman, said he had another potentially damaging photograph of Weiner but would not release it "to save his family."
ABC News reported that it had an interview with a second woman claiming a "sexually charged electronic relationship" with Weiner. She was identified as a 26-year-old single mother in Texas, apparently the same person from whom Breitbart obtained the photo of Weiner bare-chested. ABC said the woman had provided photos, emails and Facebook messages, and that her interactions with Weiner had begun April 20.
Weiner's voice broke nearly every time he mentioned his wife, Huma Abedin, an assistant to Secretary of State Hillary Rodham Clinton. Former President Clinton officiated at the couple's lavish Long Island wedding July 10.
"My wife is a remarkable woman," said a contrite Weiner, who is often described as brash bordering on arrogant. "She is not responsible for any of this and I apologize to her, very deeply."
Breitbart, who lives in Los Angeles, was in New York for a media appearance. He learned of Weiner's news conference from his business partner moments after checking into a New York hotel four blocks away, and hurried over.
Minutes after Breitbart strode off, Weiner followed him to the lectern and took blame for sending sexually suggestive photographs and comments to at least six of his female Twitter and Facebook fans. He said he had never had sex with them, nor had he met them in person.
He apologized to Breitbart.
The effect the scandal will have on Weiner's career is hard to predict. The seven-term congressman has repeatedly won reelection in his Brooklyn and Queens district by a wide margin.
Hank Sheinkof, a longtime New York Democratic strategist, said Weiner had ruined his chances to succeed New York Mayor Michael R. Bloomberg. "It's too embarrassing," Sheinkof said. "The requirements for the second-toughest job in America do not include sexting."
Lee Miringoff, director of Marist College's Institute for Public Opinion, agreed that the scandal has probably derailed Weiner's mayoral aspirations -- but maybe only temporarily.
"Any time you're in the same paragraph as Arnold Schwarzenegger, John Edwards, Eliot Spitzer it's not a good gang to be a part of," Miringoff said. But if voters like you, he said, citing President Clinton's travails, they can forgive.
"Voters can draw the line between doing a good job and a character flaw," Miringoff said. "So I think it's very important for him to stress the going-back-to-work notion."
Queens borough President Helen Marshall said she would continue to support Weiner. "I sat beside him for 10 years and I believe that everyone is entitled to one mistake," she said. "I believe that the one woman he has to answer to is his wife."
Abcarian reported from Los Angeles, and Susman from New York. Times staff writers Geraldine Baum in New York and Lisa Mascaro in the Washington bureau contributed to this report.