Updated: April 25, 6:04 p.m.Democracy 21 and other good-government groups are expected to ask the House ethics committee next week for an investigation into lawmakers with close ties to defunct lobbying firm PMA Group, Democracy 21 President Fred Wertheimer said on Friday. The request will seek a probe into whether the millions of dollars in campaign contributions the firm generated for favored Members of Congress influenced the tens of millions of dollars in earmarks those lawmakers secured for PMA clients. Outside groups are barred from filing complaints with the ethics committee, but the panel can initiate probes on its own and the request is sure to pile political pressure on an already strained House Democratic leadership team. Democratic leaders have remained in a defensive crouch in the wake of reports that federal investigators are probing the earmark empire of Rep. John Murtha (D-Pa.), the defense-spending chief in the House and a close confidant of Speaker Nancy Pelosi (D-Calif.). But that position is becoming increasingly difficult to maintain. Since news broke in February that federal agents raided the offices of the PMA Group and the home of its founder, former House Appropriations Subcommittee on Defense aide Paul Magliocchetti, Rep. Jeff Flake (R-Ariz.) has kept the issue front and center by calling votes on whether to force an ethics probe. His first attempt gathered 17 votes from the majority party, but Democratic defections on subsequent votes have mounted, reaching 27 on his seventh and latest attempt before the spring recess. Those numbers reflect growing anxiety among rank-and-file House Democrats about the ongoing federal probe and the political risk associated with failing to confront it. At a closed-door meeting before the break, Pelosi enlisted Rep. Howard Berman (Calif.), formerly the top Democrat on the ethics committee, to brief lawmakers on why they should continue to resist Flakes efforts to force a probe. And Berman is expected to reprise the briefing at a longer session, though no date for that has been set yet. Democrats throughout the Caucus, however, are privately suggesting a briefing is not enough and have begun agitating for the cover an announced ethics investigation would provide, as it did in the case of Ways and Means Chairman Charlie Rangel (D-N.Y.). The Committee on Standards of Official Conduct, as the ethics panel is formally known, is not required to disclose an investigation until a Member has been legally charged with wrongdoing, so it could have already started a probe a fact House Majority Leader Steny Hoyer (D-Md.) noted this week. I have no reason to believe the process is not working as I would hope it would, Hoyer said in an interview with The Hill that was broadcast on C-SPAN. Hoyer said he was not worried that the appearance of mounting ethical woes would taint the Democratic brand, pointing to policy goals the majority is achieving and the process reforms the party has already instituted. Im not concerned because I think we are moving the country in a new direction, a direction the American people are supportive of, he said. Murtha challenged Hoyer for the Majority Leader position at the beginning of the 110th Congress.