After a series of articles noting the November FBI raid of the offices of the PMA Group, a Washington lobby shop tightly connected to House Defense Appropriations Subcommittee Chair John Murtha, the New York Times reveals that a prominent lobbyist at PMA is under investigation for funneling fraudulent campaign contributions to Rep. Murtha and other lawmakers. That “prominent lobbyist” is former Murtha staffer and lead PMA lobbyist Paul Magliocchetti and those other lawmakers are likely Reps. Pete Visclosky and James Moran.

This marks the fourth major earmarking investigation launched against top appropriators in Congress, with many more related scandals along the way. The first large investigation netted the most extreme case of quid pro quo, Rep. Randy “Duke” Cunningham. Cunningham was found guilty of corruption for trading earmarks to defense contractors in exchange for a variety of items including a yacht, an 1850 Louis Phillipe commode, and prostitutes. The next two investigations were of the more common variety, the typical tightrope walk of lobbyists selling earmarks by navigating that fine line between serving the public interest and quid pro quo. Appropriators and lobbyists have practiced this walk for many years, and like political Phillipe Petit’s, they rarely fall. The investigations begun between 2005 and 2006 into Reps. Alan Mollohan and Jerry Lewis, both Appropriations Committee members, remain unresolved. Similar controversies have arisen around Reps. Don Young, Charles Rangel, and Curt Weldon (defeated for election in 2006) and former Sen. Ted Stevens (defeated in 2008).

The lack of resolution in these cases bodes well for the staying power of the lawmakers who appear likely to get caught up in this scandal, but it doesn’t look great for Congress’ means of appropriating money. Since the earmarking phenomenon exploded into these series of investigations (and other scandals), it has become clear that lawmakers and lobbyists have been playing a game that borders on, and often crosses into, corruption of a public office.

Robert Kaiser’s new book So Damn Much Money lays out the history of the lobbyist role in the creation of the system of directed spending that we call earmarking. One key point that comes out of Kaiser’s book is that this quid pro quo tightrope walk existed from the get-go. Earmarking was always a precarious game of greying ethical, and legal, boundaries. With the revelation of the investigation of PMA Group, a major earmark player, and their possible involvement with three long term, major appropriators, the legal system appears to have caught up with the tightrope walk.

As noted above, those under investigation, or convicted, for earmarking abuses are all long term, powerful Appropriations Committee members. Below is a chart of these members and others who face questions about their earmarking (let me know who I missed in the comments):