Foley announced through his lawyer that he had been battling alcoholism and had checked into an unidentified rehabilitation facility for treatment over the weekend.
"I strongly believe that I am an alcoholic and have accepted the need for immediate treatment for alcoholism and other behavioral problems," Foley said. "I deeply regret and accept full responsibility for the harm I have caused."
Florida Republicans picked state Rep. Joe Negron to replace Foley as the party's candidate in the West Palm Beach district, which is largely Republican.
The FBI has opened a preliminary inquiry to determine whether Foley's sexually suggestive e-mails violated federal law. Foley abruptly resigned from Congress on Friday after reports surfaced that he'd sent sexually charged electronic messages to boys working as pages.
Several pages have said Foley paid them a great deal of attention, more than his colleagues, in fact.
"Congressman Foley, I would say, was the winner in knowing the most pages and knowing them on a first-name basis," Blake Yocom, a former page, told CBS News correspondent Sharyl Attkisson.
Yocom was a page in 2003. He says at the time he wrote off Foley's interest in him and his young colleagues as overly friendly ... but it's much creepier in retrospect.
"A few of my close friends, pages, suspected that Congressman Foley was a homosexual. But we never expected pedophilia out of Congressman Foley," he told CBS News.
Foley was so interested in the page program that he once praised them in a tearful speech on the House floor as their time in Washington ended. Speaking in 2002 about a contest where the pages bid for the privilege of lunch with him, Foley said he and a page who won the bid headed for Mortons for lunch, together. "And so we proceeded to cruise down in my BMW to Morton's. And all of this story is meant to make you all feel jealous that you were not the high bidders," Foley said.
The FBI may not have seen it, but some 16-year olds sensed Foley was crossing a line that other Congressmen didn't.
"I have friends, Matt and Tim, and he would always see them first and say 'Hi, Matty. Hi, Timmy.' And we'd say 'That's pretty funny of him to say that, you know, that's kind of weird," Jenna Kelsey, a former House Page, told CBS News.
The Washington Post also reported that Patrick McDonald, a former House page, said that he had learned that three or four pages in his 2001-2002 class had received inappropriate e-mails from Foley.
McDonald, 21, said he had seen Foley e-mails sent to another page during a 2003 page reunion and recalled saying, "If this gets out, it will destroy him."
CBS News correspondent Bob Fuss reports that there are indications that members of the House leadership — all the way up to Speaker Dennis Hastert — were told about this more than a year ago. While they will admit they knew about the inappropriate e-mails, they say they never knew anything about sexually explicit ones.
"If it's proven that leaders in Congress did nothing, nothing to protect those children — those 15- and 16-year-olds — those members of Congress should resign their leadership positions," Rep. Sherrod Brown, D-Ohio, said, CBS News' Aleen Sirgany reports.
House Republicans, meanwhile, scrambled to limit political damage from the unfolding scandal following news that House leaders knew for months about Foley's inappropriate overtures toward the pages.
Hastert said Monday that no Republican leaders saw lurid Internet exchanges from Foley to pages and that he would have demanded the Florida Republican's expulsion if he had known about them.
"As a parent and speaker of the House, I am disgusted," Hastert, R-Ill., told reporters after holding a meeting at the Capitol in the wake of the disclosure of the e-mails in 2003 to a page, which led to Foley's resignation last Friday.