Abramoff's assistance led to other corruption convictions
Former Washington lobbyist Jack Abramoff has been sentenced to four years in prison for corruption.
Abramoff had pleaded guilty in a Washington court to charges of trading expensive gifts, meals and sports trips in exchange for political favours.
The case caused a scandal in Washington and sparked off a wide-ranging public corruption probe.
Abramoff is already serving a six-year term for his role in an unrelated fraudulent Florida casino deal.
The court had heard how Abramoff made tens of millions of dollars by steering clients to consultants who charged excessive fees and then split the profits with him.
Abramoff had faced a possible 11-year sentence but was shown leniency because of his cooperation in other corruption cases.
In 3,000 hours of interviews with the FBI, he gave information leading to the conviction of a string of lawmakers and high-profile political figures, including one member of Congress.
Abramoff told the court that he was "a broken man" and pleaded for leniency, saying it was "amazing for me to see how far I strayed and how I did not see it at the time".
He said that much of the activity of Washington "lives in the loopholes" but that he had "blundered farther than even those excesses would allow".
The BBC's Richard Lister in Washington says that the scandal was a disaster for the Republican party, leading to their loss of control in Congress in 2006.
But, our correspondent says, the case is unlikely to have any impact on the current race for the White House.
Abramoff's current jail term relates to the faking of a wire transfer to obtain loans to buy a fleet of casino boats.