After months of trying, U.S. House Republicans have scored a hit on Democratic counterparts, forcing the Ethics Committee to confirm that it is examining the tie between earmarks and campaign contributions.

The "review," as it was termed, was confirmed in a joint statement by Reps. Zoe Lofgren, D-Calif., and Jo Bonner, R-Ala., and added that the committee would release future statements as appropriate.

The acknowledgment marks the latest turn in what some reformers call pay-to-play politics in which powerful members of Congress target spending for firms in their districts and, in turn, receive a steady stream of cash donations for their re-election campaigns.

While the committee said the review covers an estimated 100 members, the push for an ethics probe has centered on a now-defunct defense lobbying firm and three prominent Democratic members of the House Appropriations Committee: John P. Murtha, D-Johnstown; Pete Visclosky, D-Ind.; and James Moran, D-Va.

The Center for Responsive Politics, which tracks campaign donations, estimated that Mr. Murtha has received $2.37 million from former lobbying firm PMA Group and companies it represented since 1989. The center put the figures for Mr. Visclosky at $1.36 million and for Mr. Moran at $997,000.

PMA was founded by Pittsburgh native Paul Magliocchetti, a former Appropriations Committee staff member and friend of Mr. Murtha. In November, as Mr. Magliocchetti was preparing to retire and sell the company to several associates, federal agents executed a search warrant on the company's northern Virginia offices.

Sources close to the probe have said Mr. Magliocchetti and the firm are under investigation for possibly funneling donations to congressional campaigns using straw donors.

Mr. Murtha has not been implicated in that scheme, although one source close to Mr. Magliocchetti said investigators have asked general "fishing"-type questions about him.

Mr. Visclosky's office recently confirmed that he and his former chief of staff have both been subpoenaed in the investigation and Mr. Visclosky has retained a criminal defense attorney.

The announcement of the review followed months of maneuvering by Rep. Jeff Flake, R-Ariz., who has offered a bill to forbid legislators from accepting campaign donations from any earmark recipient.

"I'm encouraged that the Ethics Committee is looking into the PMA scandal," Mr. Flake said yesterday.

Mr. Flake had been the regular sponsor of a resolution calling for the Ethics Committee to investigate earmarks and their ties to lobbyists; the votes that were repeatedly tabled. In recent months, more and more first- and second-term Democratic House members voted for that resolution.

Democrats responded last month with a pre-emptive motion calling on the committee to confirm whether it was already investigating the matter, prompting Thursday's announcement.

A spokesman for Mr. Murtha declined to comment.