And when the aide left to start his lobbying firm in 1989, he helped Mr. Murtha recruit major military contractors to attend a new annual trade fair in Johnstown that became the cornerstone of the lawmaker’s effort to steer business to the area.

Mr. Magliocchetti set up shop at the busy intersection between political fund-raising and taxpayer spending, directing tens of millions of dollars in contributions to lawmakers while steering hundreds of millions of dollars in earmarked contracts back to his clients.

Since 1998, for example, employees of the firm and its clients have contributed more than $40 million to lawmakers, including more than $7.8 million to members on the House defense spending panel and $2.4 million to Mr. Murtha, its chairman. The same lawmakers, meanwhile, have helped finance hundreds of pet projects sought by PMA clients, including earmarks for more than $300 million in the military spending bill passed last year alone. And PMA, still owned by Mr. Magliocchetti until its collapse, grew into a K Street powerhouse with more than $15 million a year in lobbying fees.

Questionable contributions linked to PMA employees appear to be one subject of the federal investigation, which came to light with reports that teams of F.B.I. agents had searched Mr. Magliocchetti’s home and the offices of PMA in Northern Virginia in November. For example, lawmakers have reported more than $150,000 in tandem contributions over the last four years from the sommelier, John Pugliese, and the golf club marketing director, Jon Walker, both of whom live near Mr. Magliocchetti’s Florida vacation home and are sometimes listed as PMA employees. Campaign finance reports include another $1.5 million since 2000 from Mr. Magliocchetti’s family. And about $95,000 over the last three years was credited to Julie Giardina, a 30-year-old lobbyist who joined PMA after a stint as a Defense Department employee working for Mr. Murtha’s staff.

None of the reported donors returned repeated telephone calls.

Accepting such contributions, however, poses relatively little risk for lawmakers unless prosecutors can prove knowing complicity in the scheme, ethics lawyers say. Enjoying Mr. Magliocchetti’s personal hospitality, on the other hand, could bring an ethics rebuke or more serious accusations of favor-trading.

Friends and veteran military industry lobbyists say Mr. Magliocchetti acquired his taste for the high life as a Congressional staff member wined and dined by lobbyists in the era before strict ethics rules. In addition to his habit of ordering tables of food from the Alpine kitchen  a lobbyist would pick up the tab  Mr. Magliocchetti picked up a taste for gumbo on visits to shipbuilders around New Orleans, and a fondness for cowboy boots from former Representative Charlie Wilson of Texas (the “good-time Charlie” whose energetic nightlife was the subject of the recent film “Charlie Wilson’s War”).

The background of a December 2001 article in Vanity Fair about the social life of a young Congressional aide captured a snapshot of Mr. Magliocchetti in his element. Two days after the Sept. 11 attacks, he and a PMA colleague, Daniel Cunningham, were hosting a rowdy table of lawmakers at dinner in a private room in the Capital Grille that included Representatives Mike Doyle, Tim Holden and Robert A. Brady of Pennsylvania; Representative Bill Pascrell Jr. of New Jersey; Representative Michael E. Capuano of Massachusetts; Representative John B. Larson of Connecticut; and former Representative John Baldacci of Maine, now governor. (Mr. Larson reportedly led the group in a sing-a-long of Beatles, Frank Sinatra and Rolling Stones songs.) All were members of an informal group that followed Mr. Murtha’s lead. Asked recently about the night, representatives of the lawmakers declined to comment..