For the third time in as many weeks, House lawmakers rejected Tuesday a resolution demanding an ethics committee investigation targeting the PMA Group, a defense lobbying firm whose robust campaign contributions appear to be at the center of a federal probe.Rep. Jeff Flake (R-Ariz.) has forced the issue to the House floor in recent weeks using privileged resolutions, asserting that the Committee on Standards of Official Conduct should investigate the firm and its relationship to Members, even as the Justice Department conducts its own inquiry.Flake’s resolution calls for the ethics panel to focus specifically on earmark requests for the clients of PMA Group and related campaign contributions.The resolution was tabled by a vote of 228-184. Flake’s previous attempt was similarly tabled, 222-181.