Abramoff has been co-operating in a wider inquiry
The case of disgraced US lobbyist Jack Abramoff has sparked off a wide-ranging public corruption probe that could have huge legal and political consequences for politicians in both houses of Congress.
As a court sentenced Abramoff to five years and 10 months for fraud and conspiracy in the SunCruz Casinos case, one of the two cases that signalled his downfall, the BBC answers some key questions about the affair.
Who is Jack Abramoff?
Until 2004, Jack Abramoff, 46, was one of the most powerful lobbyists in Washington DC, a city crowded with more than 27,500 such "policy consultants" who legally seek to persuade politicians to vote on legislation in a way that favours the interest they represent.
As a student, Abramoff was a leading Republican activist and in the course of his career developed close ties to Republican and conservative leaders. It was these ties that gave him the leverage to collect tens of millions of dollars from clients such as casino-rich American Indian tribes, who sought his influence.
Investigations into his activities were launched in 2004, after reports that he and a partner, Michael Scanlon, had received at least $45m (£26m) from tribes with casinos.
It emerged that Abramoff treated politicians and their staff to lavish meals, trips, sporting events and directed the tribes to donate millions of dollars to political candidates and parties.
What are his crimes?
On 3 January 2006, Abramoff pleaded guilty to defrauding the Native American tribes that were his clients, to tax evasion and to conspiring to bribe public officials.
A day later, he pleaded guilty in a separate case in Miami, Florida. Abramoff admitted that he and co-defendant Adam Kidan engaged in conspiracy and wire fraud in the purchase of a fleet of casino boats in 2000.
They presented lenders with a counterfeit document showing they had put $23m ($13m) into the SunCruz Casinos deal, but in fact had put virtually no money into the purchase, and the cruise line went bankrupt the following year.
Abramoff was sentenced to 70 months in jail.
What are the wider implications?
Part of the deal under which Abramoff pleaded guilty required him to co-operate in a Department of Justice investigation into his dealings with members of Congress.
This separate case is believed to be focusing on as many as 20 lawmakers and their aides.
Among the areas it will examine are whether gifts to politicians influenced their actions in Congress, and whether they followed the rules in disclosing what had been given to them.
Abramoff has apparently promised to reveal not just who was paid and how much, but also what the understandings were that led to the transfer of favours and money.
If he claims credibly that he was expecting political action to be taken in return for cash, then a number of senior politicians may have committed serious crimes and could end up in jail.
What has Congress done about the scandal?
The scandal put the sometimes murky world of lobbying under the microscope like never before.
A number of anti-corruption reforms were subsequently put on the table by members of Congress from both sides of the political divide.
But the swift and bold action promised amid the heat of the scandal have yet to materialise.
A Senate bill, which has bipartisan support, would require greater disclosure of lobbyists' activities, stop senators from accepting meals from lobbyists, introduce greater scrutiny of trips paid for by provide sponsors and slow the movement of lawmakers to lobbying jobs.
It also provides a way to kill pet projects - or pork barrel spending - that lawmakers sneak into larger bills.
Yet the bill has slipped from the Senate schedule. Legislation in the House has also slowed, although it is thought a bill may be moved before the Easter recess, and among other measures contain a temporary ban on privately funded travel.
How will it affect the mid-term elections?
Democrats believe Republicans will bear the brunt of the political fallout from the Abramoff affair.
They also see the issue of what they say is a Republican party tainted by corruption as a vote-winner in November's mid-term elections
As well as the Abramoff scandal, other corruption-related incidents have taken a toll on the ruling party's standing.
Republican Tom DeLay resigned as House majority leader after he was indicted in Texas over a campaign financing case.
Lewis Libby - Vice-President Dick Cheney's former chief of staff - faces trial next January on charges relating to the leaking of a CIA agent's identity to the press.
Meanwhile, Bill Frist, the Senate majority leader, is under scrutiny by the Security and Exchange Commission over share dealings.
And in March 2006, Republican Congressman Randy Cunningham was sentenced to eight years in jail for taking $2.4m (£1.4m) in bribes from a defence contractor.