Rep. Michael P. Forbes (R-N.Y.) will announce this afternoon that he is switching parties, according to several sources.

Calls to Forbes's office and home were not returned, but informed sources said he would hold a 1 p.m. news conference at his Long Island home to declare his decision to become a Democrat. He flew there from Washington in a private jet accompanied by a Democratic Congressional Campaign Committee official, sources said, after meeting with House Minority Leader Richard A. Gephardt (D-Mo.) yesterday afternoon.

The move would be the latest act of rebellion by the three-term suburban Republican, who turned 47 yesterday and has had a combative relationship with the Republican leadership since late 1996.

A member of the revolutionary freshman class of 1994, Forbes unseated a Democrat and was rewarded with a spot on the prized House Appropriations Committee. While he loyally supported the GOP's "Contract With America" after he arrived in Washington, he gradually began taking more centrist stands on issues such as health care and campaign finance.

While several House Democrats have switched parties since the GOP won the majority, including Reps. Nathan Deal (Ga.) and W.J. "Billy" Tauzin (La.) and former representatives Mike Parker (Miss.) and Greg Laughlin (Tex.), the idea of a lawmaker choosing to join the minority has taken House Republicans by surprise. Since 1981, 11 House members and two senators, all Democrats, have switched parties to become Republicans. National Republican Congressional Committee Chairman Thomas M. Davis III (Va.) confronted Forbes about the rumors concerning his potential switch several times this week, according to sources, and as recently as Thursday Forbes denied to Davis that he was leaving the party.

News of the impending switch prompted immediate GOP criticism. "If he wants to take Americans back to the days of high taxation, high deficits, bloated bureaucracy and the welfare state, then he's joining the right team," said NRCC spokeswoman Jill Schroeder.

It is unclear what impact the switch will have on Forbes's political standing in New York's 1st Congressional District. A former congressional aide and Small Business Administration regional administrator, Forbes has solidified his hold over the GOP-leaning district over the years, winning 64 percent of the vote last year.

His most significant break with the party came in December 1996, when he said he believed House Speaker Newt Gingrich (R-Ga.) should step down because of his ethics troubles. On the opening day of the 105th Congress, Forbes voted for Banking and Financial Services Committee Chairman Jim Leach (R-Iowa) for speaker rather than Gingrich, incurring the wrath of Gingrich loyalists.

During the summer of 1997, Forbes participated in an aborted coup against Gingrich, becoming even more marginalized in the House. "The prom king and queen don't want to be seen talking to me," he told the New York Times in 1997, referring to a politically powerful New York Republican couple, then-Rep. Bill Paxon and his wife, former representative Susan Molinari.

Forbes later angered Republicans by appearing publicly with President Clinton at a 1998 news conference to endorse the Democrats' version of managed-care reform, as well as by giving Democratic Rep. Loretta Sanchez (Calif.) a $1,000 contribution in her high-profile rematch against Republican former representative Robert K. Dornan.

His political fortunes changed rapidly after the 1998 elections, when the GOP's poor showing prompted then-Rep. Bob Livingston (R-La.) to challenge Gingrich for the speakership, a move that prompted Gingrich's resignation.

Livingston had announced months earlier that he would run for speaker once Gingrich stepped down, and Forbes had worked tirelessly to promote Livingston's candidacy, collecting funds from the Washington lobbying community.

As one of Livingston's closest allies, Forbes enjoyed newfound power and started toeing the GOP line more faithfully. Although he had indicated privately after the election he would not vote to impeach Clinton, he decided shortly before the House voted on Dec. 19 to support all four counts of impeachment against the president.

That same day, however, Forbes lost his political patron when Livingston decided to resign after admitting he had engaged in several extramarital affairs.

Although he recently endorsed Texas Gov. George W. Bush for president, Forbes nevertheless then bucked his party again. Just this week, he supported Appropriations Committee Democrats' unsuccessful attempts to attach three gun control provisions to a bill providing funding for the Treasury Department and the Postal Service.