WASHINGTON, Dec. 1 - With a federal corruption case intensifying, prosecutors investigating Jack Abramoff, the Republican lobbyist, are examining whether he brokered lucrative jobs for Congressional aides at powerful lobbying firms in exchange for legislative favors, people involved in the case have said.

The attention paid to how the aides obtained jobs occurs as Mr. Abramoff is under mounting pressure to cooperate with prosecutors as they consider a case against lawmakers. Participants in the case, who insisted on anonymity because the investigation is secret, said he could try to reach a deal in the next six weeks.

Many forces are bearing down on Mr. Abramoff. Last week, his closest business partner, Michael Scanlon, pleaded guilty to conspiracy in exchange for cooperating in the inquiry, being run by an interagency group, into whether money and gifts were used in an influence-peddling scandal that involved lawmakers.

Despite charging Indian tribes that were clients tens of millions of dollars in lobbying fees, Mr. Abramoff has told friends that he is running out of money. In a new approach that could contribute to the pressures, prosecutors are sifting through evidence related to the hiring of several former Congressional aides by a lobbying firm, Greenberg Traurig, where Mr. Abramoff worked from 2000 to last year, according to people who know about the inquiry. That course could impel a new set of Mr. Abramoff's former associates to cooperate to avoid prosecution.

Investigators are said to be especially interested in how Tony C. Rudy, a former deputy chief of staff to Representative Tom DeLay of Texas, and Neil G. Volz, a former chief of staff to Representative BobNey of Ohio, obtained lobbying positions with big firms on K Street.

The hiring pattern is "very much a part of" what prosecutors are focusing on, a person involved in the case said. Another participant confirmed that investigators were trying to determine whether aides conducted "job negotiations with Jack Abramoff" while they were in a position to help him on Capitol Hill.

Prosecutors are trying to establish that "it's not just a ticket to a ballgame, it's major jobs" that exchanged hands, the participant in the case said. Also under examination are payments to lobbyists and lawmakers' wives, including Mr. Rudy's wife, Lisa Rudy, whose firm, Liberty Consulting, worked in consultation with Mr. Abramoff, people involved in case said.

What began as an inquiry into Mr. Scanlon and Mr. Abramoff's lobbying has widened to a corruption investigation centering mainly on Republican lawmakers who came to power as part of the conservative revolution of the 1990's. At least six members of Congress are in the scope of the inquiry, with an additional 12 or so former aides being examined to determine whether they gave Mr. Abramoff legislative help in exchange for campaign donations, lavish trips and gifts.

It may be difficult for prosecutors to translate certain elements of the case into indictments. Bribery, corruption and conspiracy cases are notoriously difficult to prove. But the potential dimensions are enormous, and the investigation, at a time of turmoil for the Bush administration, threatens to add a new knot of problems for the party heading into the elections next year.

Several people involved in the case, insisting on anonymity because of the plea negotiations, said they anticipated that Mr. Abramoff would try to reach an agreement with the prosecutors in a rapidly closing window of time before he is scheduled to stand trial in a separate federal case in Florida.

Mr. Abramoff and another business partner, Adam Kidan, were indicted in August on charges of wire fraud and conspiracy for reportedly defrauding their lenders as they sought to buy a company in Miami, SunCruz Casinos, that operated a fleet of gambling boats.

That trial is to begin on Jan. 9.

A lawyer for Mr. Abramoff in the case, Neal R. Sonnett, declined to comment on whether his client is conferring with prosecutors, indicating that he is moving ahead as though there will be no plea agreement.

"I'm preparing for trial," Mr. Sonnett said.

After more than a year of slow progress in what initially appeared to be a case of lobbying excess, the larger scope of the inquiry started to come into view toward the end of September with the arrest of David H. Safavian, chief procurement official in the administration.

Mr. Safavian is accused of lying to investigators and of obstruction of justice. He is pleading not guilty, his lawyer has said. Prosecutors contend that Mr. Safavian did not disclose to investigators business that Mr. Abramoff had before his agency at the time of a golfing trip to Scotland arranged by the lobbyist.

The focus also expanded from Mr. Abramoff's work for Indian tribes with the end of hearings by the Senate Indian Affairs Committee. The hearings set out to examine whether the tribes, which paid $82 million to Mr. Abramoff and Mr. Scanlon, had been defrauded. The panel, headed by Senator John McCain, Republican of Arizona, avoided looking at the ties between the lobbyists and specific lawmakers, leaving that to the inquiry's interagency group.

The Senate hearings uncovered many patterns of Mr. Abramoff's activities, including his offering favors to officials while making deals on government work. In one case, a former senior Interior Department official, J. Steven Griles, testified that Mr. Abramoff had offered him a position at Greenberg Traurig while Mr. Griles was in a position to affect decisions involving Mr. Abramoff's Indian clients. Mr. Griles said he reported the offer to his department's ethics division and rejected it.

Prosecutors are trying to determine whether Mr. Abramoff made similar overtures to other well positioned government workers, especially former aides to Republican leaders in of the House and Senate. Such gestures could be considered as bribery or a conflict of interest, especially if the interests of the two parties were entangled.

Of particular interest, according to several people involved in the case, are how Mr. Rudy, who left Mr. DeLay's office in 2001 to join Greenberg Traurig, and Mr. Volz, who left Mr. Ney's office in 2002 for that firm, obtained their positions. Investigators believe Mr. Abramoff may have solicited help from both men and their supervisors on Capitol Hill while helping arrange for high-paying positions, people familiar with case said.

Mr. Rudy now works for the Alexander Strategy Group, a lobbying firm run by Ed Buckham, another former senior aide to Mr. DeLay. Alexander Strategy is also under scrutiny for its ties to Mr. Abramoff and for putting Mr. DeLay's wife, Christine, on its payroll for several years.

As investigators try to unravel the web of relationships between the lawmakers and the lobbyists, they are considering spouses' roles, people involved in the case said.

Neither Mr. Rudy nor Mr. Volz returned calls and e-mail messages seeking comment on Thursday.

Hiring patterns offer a rich and complicated field for investigators. Congressional staff members routinely leave for the private work, with the sole prohibition a one-year ban on lobbying their former supervisors. Mr. DeLay is so renowned for funneling his skilled staff members into lobbying firms across Washington that his political network is known as "DeLay Inc."

Although Mr. DeLay was reprimanded by the House Ethics Committee in the late 90's for pressuring a lobbying firm to hire a Republican, the practice has become so standard in an era of Republican dominance that partisans have given it a name, the K Street Project.

What investigators seek is evidence of a quid pro quo between Mr. Abramoff and the lobbyists he helped hire, lawyers and others involved in the case said. They are especially interested in evidence that Mr. Abramoff discussed hiring Mr. Rudy, Mr. Volz or other staff members before they left the government or around the time they or their bosses were doing favors for Mr. Abramoff's clients.

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