House Democrats breathed a sigh of relief last week when the ethics committee confirmed an investigation that likely centers on some of the party’s most senior appropriators.

The reaction was a testament to the success of the Republican pressure campaign to keep the heat on Democrats for dragging their feet on confronting the mounting controversy. With the official word that the Committee on Standards of Official Conduct is in fact probing lawmakers’ ties to the PMA Group, the majority no longer has to worry about beating back a series of resolutions from Rep. Jeff Flake (R-Ariz.) aimed at forcing an investigation.

Since February, Flake has tied Democrats in knots with the gambit, peeling off a slowly mounting number of their Members — mostly freshmen and sophomores — and continuing the ethics headache for leaders trying to tackle a sweeping agenda.

“It is a relief,— one senior Democratic aide said. “Now Flake can’t come back and say, Why isn’t ethics doing its work, and what are you hiding behind?’—

The ethics committee announcement came about a week after House Majority Leader Steny Hoyer (D-Md.) engineered a resolution calling on the panel to disclose within 45 days whether it was looking into the PMA scandal.

While the ethics announcement may mark the end of the Flake resolutions, Republicans don’t intend to allow Democrats even a short-term reprieve. This week, for example, Rep. Mark Kirk (R-Ill.) said he plans to offer amendments in the Appropriations Committee, and potentially on the floor, that would rescind funding for earmarks included in the omnibus spending bill earlier this year that were directed to the clients of PMA, a now-defunct lobbying group.

“We ought to postpone spending the money until we see the outcome of the criminal investigation and now the ethics committee investigation,— Kirk said, adding that PMA had become a cloud over the Congress that can no longer be ignored. “We are reaching a tipping point on this.—

And Flake signaled he would use the news out of the ethics committee to argue for suspending earmarks to private companies and to ban campaign contributions from earmark recipients.

But the longer-term threat comes from the scandal itself.

The Justice Department is in the midst of a months-long investigation of PMA, which has close ties to Democratic Reps. John Murtha (Pa.), Peter Visclosky (Ind.) and Jim Moran (Va.). The firm and its clients generated millions of dollars in campaign contributions for the lawmakers, who secured tens of millions of dollars in projects for the shop’s clients.

Federal agents raided PMA’s Arlington, Va., offices in November, and the firm folded earlier this year. The probe officially landed on Capitol Hill late last month, when Visclosky disclosed that his Congressional and campaign offices, as well as some aides, had been subpoenaed as part of a federal grand jury investigation.

Regardless of what, if anything, the ethics committee review turns up, the federal investigation appears to be proceeding apace — and that’s what should keep the party on edge, said Melanie Sloan, executive director of Citizens for Responsibility and Ethics in Washington. “Does this give Democrats cover? No. PMA is going to blow up — it’s going to get much worse than it is now,— she said, dismissing the announcement from the ethics committee as “theater.—

Democrats privately acknowledged there is little they can do to stem the fallout from the ongoing federal probe. But they argued they can now point to the fact of the ethics investigation as evidence that the institutional process for self-policing is functioning — a distinction from the years of Republican rule when the committee remain deadlocked and effectively dormant.

“The system is working,— said Nadeam Elshami, spokesman for Speaker Nancy Pelosi (D-Calif.). “The ethics committee is conducting its business in a bipartisan way.—

Likewise, Rep. Chellie Pingree (D-Maine), a freshman and former director of the government watchdog group Common Cause, said the committee’s announcement should “give people confidence that the process is working.—

Murtha, for his part, said he has yet to be contacted by the ethics panel and is not worried about potentially being the focus of its investigation.

“I do my job. I’m here to do earmarks,— the Appropriations Subcommittee on Defense chairman said. “I’m here to collect contributions. The Constitution says I can do that.—

Asked whether he is frustrated by Flake’s amendments, Murtha said no. “It’s not a pain in my side. … It’s all politics,— he said.

Meanwhile, Visclosky got an encouraging sign from the Federal Election Commission that, per his request, he would be allowed to tap his campaign funds to mount a legal defense. The FEC made the announcement in a draft advisory opinion and must still hold a formal vote to approve it.

Steven T. Dennis and Jennifer Bendery contributed to this report.