Joe Negron, the Republican candidate who was picked on Monday to replace former Rep. Mark Foley, R-Fla., began tackling the immediate problem he faces: Anyone who votes for him won't be able to see his name on the November ballot.

Instead, those voters will have to cast a vote for Foley, who resigned from the House last week amid a still unfolding scandal involving sexually explicit electronic messages he wrote to teenage male congressional pages.

"The No. 1 challenge is to inform the voters that Mark Foley is only a spot on the ballot, ... that he is simply a placeholder and that you're voting for the Republican nominee," Negron told reporters at a Florida news conference announcing the decision that he is the candidate to replace Foley.

"So my message is going to be very simple: If you support the president, if you're a Republican or a conservative Democrat, you need to vote for the Republican nominee," Negron said.

Florida Republican leaders on Monday chose the three-term state legislator as their candidate to replace Foley and face Democratic challenger Tim Mahoney for the state's 16th Congressional District, a day after Foley checked himself into an alcohol rehabilitation facility citing alcohol and psychological issues.

Party officials said it is too late to change the Florida ballot, and Foley's name — not Negron's — will appear when voters make their choice in November for the candidate to fill the seat next January. The seat will remain empty until then.

Negron also said he was hopeful of being able to free up $600,000 from Foley's campaign to fund his run. Foley's West Palm Beach district is largely Republican, but now may be won by a Democrat.

Foley abruptly quit Congress on Friday after reports surfaced that he'd sent sexually charged electronic messages to boys working as congressional pages.

Investigations by federal and congressional agencies are beginning to ramp up, and the developments have sent House Republicans, who are struggling to maintain their House majority in the upcoming election, into damage control mode.

Democrats are charging that some House GOP leaders may have known for months about Foley's inappropriate overtures toward the young pages.

But one heavyweight Republican told FOX News on Monday the efforts might not be enough. Asked if he thought that the GOP might lose Foley's seat in light of the scandal and the ballot problems, House Majority Leader John Boehner, R-Ohio, said, "I do."

Meanwhile, Foley issued a statement accepting responsibility for his actions, which were being reviewed by the for any criminal activity.

"I strongly believe that I am an alcoholic and have accepted the need for immediate treatment for alcoholism and other behavioral problems," Foley said in a statement released in Florida by his attorney, David Roth.

Roth would not identify the facility, but said Foley had checked into a facility over the weekend.

"I deeply regret and accept full responsibility for the harm I have caused," Foley said in the statement.

Broadening Investigation

Attorney General Alberto Gonzales on Monday acknowledged that his department will be investigating the matter.

"We've been asked to look at it, and we'll look at it. We'll do what we have to do," Gonzales said. He said that while there has been preliminary fact finding, the department has not yet opened a formal federal criminal investigation into Foley's conduct.

FBI spokesman Richard Kolko characterized the agency's efforts so far, saying the FBI "is conducting an assessment to see if there's been a violation of federal law," without elaborating further.

FBI cyber sleuths are looking into the text of some of the Foley messages, checking to see how many e-mails and instant electronic messages were sent and how many computers were used, according to a law enforcement official, who spoke on condition of anonymity because of the ongoing investigation.

The FBI also was trying to determine if any of the teenagers who received messages are willing to cooperate with the investigation, the official said.

Ironically, Foley, who is 52 and single, could be found to have violated a law that he helped to write as co-chairman of the Congressional Missing and Exploited Children's Caucus.

Political Outrage

House Speaker Dennis Hastert, R-Ill., issued his strongest statement yet on Monday, saying he was "outraged and disgusted with Congressman Mark Foley's actions."

The speaker was in Washington meeting with his staff, the House clerk and Rep. John Shimkus, R-Ill., the congressman who oversees the page program, to review the procedures on protecting the teenage pages while they are working at the Capitol and after they finish their assignments, said Ron Bonjean, Hastert's spokesman.

Battling accusations that he and others might have known about the explicit instant messages before they were reported last week, Hastert spoke to reporters Monday afternoon, repeating that no one in the Republican leadership was aware of the instant messages that Mark Foley apparently wrote in 2003 until it was reported last week by ABC News.

Hastert, who described the messages as "vile and repulsive" said he was glad Foley resigned, and "if he did not, I would have demanded his expulsion."

Hastert and Shimkus did not answer reporter's questions, but said they have set up a phone number that current and former pages and their family members can call with either information about Foley or concerns about the page program. The two said the page program has been increasing its security, including some measures taken after Sept. 11, 2001., "but we obviously need to do more."

Hastert also blasted those who kept the messages secret, and then called for anyone able to aid in the investigation. He said that he had also asked Florida Gov. Jeb Bush to look into any criminal activity associated with Foley's actions.

"Anyone who had knowldege of these instant messages should have turned them over to authorities immediately so that kids could be protected," Hastert said. "Again, I repeat, the Republican leaders of the House did not have them. We all said so and on the record.

"But someone did have them, and the [House] ethics committee, the Justice Department, the news media and anyone who can should help us find out who."

House Minority Leader Nancy Pelosi, responding to Hastert, said she believes House GOP leaders are not responding strongly enough and called for an investigation into how the allegations were handled.

"Speaker Hastert again failed to answer the question that every mother and father in America is asking: How could Republican leaders chose partisan politics over protecting children?

"Republican leaders admitted to knowing about Mr. Foley's abhorrent behavior for six months to a year and failed to protect the children in their trust. Republican leaders must be investigated by the Ethics Committee and immediately questioned under oath," she said.

White House press secretary Tony Snow, asked about that Monday on ABC's "Good Morning America," urged greater efforts to "figure out what happened here."

He called it "a terrible story" and said he considered it unfortunate that "people are thinking, 'OK, can I get political advantage out of this'."

Hastert sent a letter Sunday to Gonzales asking the Justice Department to "conduct an investigation of Mr. Foley's conduct with current and former House pages."

White House counsel Dan Bartlett called the allegations involving Foley shocking, while Democrats demanded that investigators determine whether Republican leaders tried to cover up Foley's actions for political reasons.

"The attorney general should open a full-scale investigation immediately," Senate Democratic leader Harry Reid of Nevada said in a statement, including whether GOP leaders "knew there was a problem and ignored it to preserve a congressional seat this election year."

Rep. Thomas Reynolds of New York, head of the House Republican election effort, said he told Hastert months ago about the allegations involving a 16-year-old boy from Louisiana.

Hastert acknowledged that his staff had been made aware of concerns about what they termed "over-friendly" e-mails Foley had sent to the teenager — including one requesting his picture — in the fall of 2005, and that they referred the matter to the House clerk.

But Hastert said those e-mails were not viewed as "sexual in nature" and that he was not aware of "a different set of communications which were sexually explicit ... which Mr. Foley reportedly sent another former page or pages."

Hastert asked the Justice Department to investigate "anyone who had specific knowledge of the content of any sexually explicit communications between Mr. Foley and any former or current House pages and what actions such individuals took, if any, to provide them to law enforcement."

Congressional pages, a staple of Washington politics since the 1820s, are high school students who serve as gofers in the House and Senate.

Republican leaders say it's their duty to ensure House pages' safety, and they're setting up a toll-free hot line for pages and their families to call to confidentially report any incidents. They also will consider adopting new rules on communications between lawmakers and pages.

FOX News' Kelly Wright, Ian McCaleb, Carl Cameron and Greg Simmons and The Associated Press contributed to this report.