In September, Mr. Boyland, a Democrat, unexpectedly backed out of a plea agreement that would have called for a nine-year prison sentence. He will almost certainly receive more time now: The convictions call for up to 30 years; he is to be sentenced on June 30.

Outside the courthouse, Loretta E. Lynch, the United States attorney for the Eastern District of New York, called the trial “a spectacle of arrogance and entitlement that has been both truly breathtaking and also profoundly sad.”

“He could have brought real jobs and development to hard working communities that need and deserve those resources,” she said. “Instead William Boyland Jr. worked to glorify one person, and that was himself.”

Mr. Boyland was first arrested in March 2011 as part of an investigation into a broad-ranging conspiracy involving a hospital executive who Manhattan prosecutors said paid several legislators for political favors. The executive, David P. Rosen, was convicted of bribing Mr. Boyland and others, but in a separate trial in November 2011, a jury found that the evidence against Mr. Boyland was circumstantial. Prosecutors showed that Mr. Boyland lobbied on behalf of the hospital group and that the group gave him a lucrative consulting job, but could not show that there was a quid pro quo.

Three weeks after the acquittal in Manhattan, Brooklyn prosecutors unsealed a criminal complaint with transcripts of Mr. Boyland asking for money. Two undercover agents with the Federal Bureau of Investigation made secret recordings of meetings with Mr. Boyland at Peter Luger Steakhouse, his district office in Brooklyn and the Tropicana Hotel in Atlantic City. Mr. Boyland, sometimes loosened by alcohol, talked effusively about deals he could help close and the powerful people he knew.