WASHINGTON — Rep. Chris Lee of New York abruptly resigned Wednesday evening, hours after a gossip website reported that the married Republican had allegedly sent flirtatious e-mail messages and a shirtless photo of himself to a woman he met online.

Lee experienced his fall from grace in a single afternoon, undone at the speed of the digital age. At lunchtime Wednesday, he was an obscure but promising second-term congressman. Then, at 2:33 p.m., Gawker.com posted an alleged e-mail exchange between a man who used Lee’s name — but identified himself as a divorced lobbyist — and an unidentified woman. Gawker reported that the two had met through the personals section of Craigslist.

After that, the familiar cycles of a Washington sex scandal were compressed into a blur of tweets and news alerts. There was confusion, a hint of denial, then a pledge from Lee to “work it out” with his wife.

By 6 p.m., a clerk was announcing Lee’s resignation in the House chamber.

“I regret the harm that my actions have caused my family, my staff and my constituents,” Lee said in a statement. “I deeply and sincerely apologize to them all. I have made profound mistakes and I promise to work as hard as I can to seek their forgiveness.”

Lee’s statement did not confirm or deny any specific allegations from the Gawker report.

Lee, 46, elected from a district in western New York, was just beginning his second term in Congress.

He had been a successful businessman and was known as an up-and-coming Republican voice on financial issues.