Rep. John Murtha has long been on good-government groups' lists of the most corrupt lawmakers in Washington. But in recent months, the veteran Pennsylvania Democratic powerbroker has been under particularly intense scrutiny for his ties to two companies that are each the targets of federal investigations.

So it's worth taking a moment to consider what's going on in each case, and what it all amounts to.

Back in February, we learned that the FBI had raided the northern Virginia office of the PMA Group, a lobbying firm that specialized in representing defense contractors looking for federal dollars. The Feds have been said to be probing whether PMA steered donations to lawmakers through sham donors, perhaps in exchange for earmarks. In the wake of that news, many of PMA's lobbyists quickly jumped ship, and the firm soon fell apart.

Murtha, who chairs the Appropriations committee's Defense subcommittee, has ties to PMA that run deep. The firm was founded in 1989 by Paul Magliocchetti, a colorful former top Murtha aide who was known for regularly wining and dining lawmakers and their aides at swank Washington eateries. And at least one other former Murtha aide, Julie Giardina, worked at the firm until recently, as did Dan Cunningham, a former Hill aide who's said to be close to Murtha.

But personal links are the least of it. Since 2002, Murtha has raked in around $1.75 million from PMA and its clients. Last fall, Murtha's re-elction bid unexpectedly grew tight after he said his constituents were racists. Who came to his rescue? PMA, which threw in $110,000 in the race's final weeks.

The generosity, of course, runs both ways. Murtha has steered earmarks totaling around $93 million to PMA clients -- and that's just in the last two years.

In fact, though, it's another Democratic lawmaker who's taken the worst toll from the PMA scandal so far. Rep. Pete Visclosky of Indiana, who chairs another appropriations sub-committee, has been subpoenaed for documents as part of the probe. In response, Visclosky has said he's handing off the lead role on a major appropriations bill to a colleague. And amid the tumult, Visclosky's chief of staff "retired" earlier this month.

Visclosky's relationship with PMA appears just as cozy as Murtha's, if not cozier. Another of his former chiefs of staff was a lobbyist for the firm, and between 2006 and 2008 Visclosky took in least $100,000 in contributions from donors tied to the firm, which has been Visclosky's top donor every year since 2004. According to the Center for Responsive Politics, only Murtha has received more money from PMA and its clients. On the other side of the coin, the lawmaker helped to secure more than $23 million in earmarks, last year alone, for clients of PMA Group.

Thanks largely to the efforts of Rep. Jeff Flake, the Arizona Republican anti-pork crusader, the House ethics panel has now joined the Feds in looking into PMA, and its ties to lawmakers. So this figures to be a long way from the last we'll hear on the issue that one good government watchdog declared earlier this year "will become the majority's Waterloo on ethics."

But for Murtha, PMA isn't the only company he's been close to that's attracting unwanted scrutiny. Last month, the Navy suspended Kuchera Defense Systems, a defense contracting firm based in Murtha's district which is being investigated by the Feds. According to reports, tips from company insiders suggest that taxpayers may have been billed improperly for Kuchera family expenses and renovations to the western Pennsylvania "ranch" that serves as the company's HQ.

Murtha has taken in more than $589,000 in contributions from Kuchera employees and their families. And CEO Bill Kuchera -- who in the 1980s reportedly helped run marijuana and cocaine from Miami to Racine, Wisc. -- served on the board of a non-profit founded by a former Murtha aide. For his part, Murtha has steered over $14 million in defense earmarks to the company in just the last two years.

In fact, though, those numbers don't get at what appear to be the chummy relationship between Murtha and Kuchera Industries. In a 2000 interview, Bill Kuchera declared: "Without Congressman Murtha, there would be no Kuchera Defense."

So what does this all amount to? It's worth being clear that no one has formally alleged any wrongdoing by Murtha or Visclosky (or any other lawmakers) in connection with PMA or Kuchera. And as a legal matter, it's generally very hard to prove an illegal quid pro quo in these sorts of cases.

Still, as an ethical issue, it's hard to deny that for lawmakers to direct that much federal money to companies that have been such significant donors to those same lawmakers hardly represents the new politics that both the Democratic Congress and President Obama have promised us.

And that's why it could soon become a political issue for Murtha's close ally, Nancy Pelosi -- one she'd certainly rather not have to deal with.