Former Gov. Eliot Spitzer was deeply involved in his administration's efforts last year to discredit the State Senate majority leader, Joseph L. Bruno, holding detailed discussions with senior aides, ordering damaging information about Mr. Bruno released, and calling an aide at home repeatedly to check on the progress, according to several people with direct knowledge of the investigation.
The governor has previously said he was not personally involved in the effort, suggesting only that he was vaguely aware that his aides had responded to a reporter's inquiry about Mr. Bruno's travels on state aircraft.
But testimony and other information gathered by the Albany County district attorney, P. David Soares, indicate that the governor's participation was extensive and reflected Mr. Spitzer's intense desire to damage Mr. Bruno, the people with knowledge of the case said.
The investigation was based on examination of e-mail messages, along with interviews with about a half-dozen senior administration officials, chief among them Mr. Spitzer's former communications director, Darren Dopp, whom prosecutors decided last month to give immunity from prosecution.
A spokeswoman for Mr. Spitzer, who resigned March 12 after reports that he had patronized a high-priced prostitution ring, could not immediately comment on Sunday night.
Heather Orth, a spokeswoman for Mr. Soares, said: "As with all cases of public integrity, we will not comment on an ongoing investigation. We expect to be completed with our investigation at the end of the month, and will report our findings then."