Washington ? A former top aide to Rep. Tom DeLay pleaded guilty Friday to conspiracy and promised to help with an investigation of bribery and lobbying fraud that already has netted three convictions and sparked calls for ethics reform in Congress.

Tony Rudy, DeLay’s former deputy chief of staff, admitted conspiring with convicted lobbyist Jack Abramoff – both while Rudy worked for the Texas congressman and after he left the lawmaker’s staff to become a lobbyist himself.

He is the second former DeLay staffer to plead guilty to federal charges in connection with the lobbying probe. The plea agreement makes no allegation that DeLay did anything wrong.

Rudy faces up to five years in prison but could receive much less based on the extent of his help with the investigation.

Court papers for the first time also referred to a third former DeLay aide, Ed Buckham. Buckham, a onetime DeLay chief of staff, is described only as Lobbyist B, but is easily identifiable because the documents say Rudy worked with him after a brief stint at Abramoff’s lobbying firm.

Beginning in 1997, Abramoff, his clients and Buckham’s clients plied Rudy with expensive meals, trips, sports tickets, golf games and clubs, according to the plea agreement filed in U.S. District Court in Washington.

Rudy also arranged payments through Abramoff and Buckham to a consulting firm that he created and his wife, Lisa, ran. Liberty Consulting received $86,000 in payments from or at the direction of Abramoff and others while Rudy worked for DeLay.

At the same time, according to the court document, Rudy agreed to “perform a series of official acts.”

These included:

l Working to get federal money for the Northern Mariana Islands, which both Abramoff and Buckham wanted.

l Getting DeLay to oppose a postal rate increase that was opposed by magazine publishers who were represented by Abramoff.

Richard Cullen, DeLay’s lawyer, called Rudy’s plea good news for his client because there is nothing in it that suggested DeLay was aware of Rudy’s actions.

Other ethics lawyers and experts, however, said the Rudy plea could be ominous for DeLay, who already is under indictment in Texas.

Prosecutors “are not going to lay out a case against him in this indictment,” said Stanley Brand, a Washington lawyer and former counsel to House Democrats. “There is a kind of well-worn method at the Justice Department to trade up by indicting the lower-downs.”