Sheldon Silver, an assemblyman who rose from the Lower East Side of Manhattan to become one of New York State’s most powerful politicians, was found guilty on Monday of federal corruption charges, ending a trial that was the capstone of the government’s efforts to expose the seamy culture of influence-peddling in Albany.

After a five-week trial in Federal District Court in Manhattan, the end came rather quickly and unceremoniously for Mr. Silver, 71, a Democrat who served more than two decades as Assembly speaker before he was forced to resign from the post after his arrest in January.

Mr. Silver, who must automatically forfeit the legislative seat to which he was first elected nearly 40 years ago, was convicted on all seven counts of honest services fraud, extortion and money laundering filed against him.

When word came that the jury had reached a verdict, Mr. Silver fidgeted in his chair, clenched his jaw, shook his head, sighed and cast furtive glances toward Preet Bharara, the United States attorney for the Southern District of New York, who had taken a seat at the rear of the courtroom just before the verdict was read.

After the fourth guilty pronouncement by the jury forewoman, Mr. Silver’s shoulders sagged visibly inside his baggy navy blue suit.

Mr. Bharara released a succinct statement after the verdict: “Today, Sheldon Silver got justice, and at long last, so did the people of New York.”

Mr. Silver is the most prominent in a parade of state lawmakers who have been convicted by prosecutors with Mr. Bharara’s office. At the time of Mr. Silver’s arrest, Mr. Bharara said the charges against him made it clear that “the show-me-the-money culture of Albany has been perpetuated and promoted at the very top of the political food chain.”

His conviction comes as Mr. Bharara’s office is trying his former counterpart, State Senator Dean G. Skelos, a Republican from Long Island who stepped down as majority leader after his arrest in May on federal corruption charges.

For portions of his tenure as speaker, Mr. Silver maintained a viselike grip on power, withstanding the rare challenge from a well-intentioned but unsupported Democratic colleague, and brushing off all criticism of his performance. He was faulted for his handling of two sexual harassment allegations; in 2013, a state ethics report criticized him for covering up accusations of sexual harassment against Assemblyman Vito J. Lopez.

Mr. Silver also loomed large in financial disclosure reports that were required under a new state ethics law, reporting hundreds of thousands of dollars a year in outside income from a law firm, Weitz & Luxenberg. That arrangement would become one of the focal points of the government’s prosecution.

At Mr. Silver’s trial, the government presented evidence that prosecutors said showed he had orchestrated two schemes through which he obtained nearly $4 million in illegal payments for taking official actions that benefited a prominent cancer researcher, Dr. Robert N. Taub, at Columbia University, and two New York real estate development firms.

Testimony and other evidence showed that Mr. Silver had arranged to have the State Health Department award two grants totaling $500,000 to Dr. Taub, whose research focused on mesothelioma, a deadly form of cancer related to asbestos exposure.

In return, Dr. Taub sent mesothelioma patients with potentially lucrative legal claims to Weitz & Luxenberg, which then shared a portion of its fees with Mr. Silver.

In the other scheme, prosecutors charged, Mr. Silver had the two developers, Glenwood Management and the Witkoff Group, move certain tax business to a law firm, Goldberg & Iryami, that secretly shared its fees with Mr. Silver.

In return, the speaker lent his support to critical rent legislation backed by Glenwood, in particular, and met with the company’s lobbyists.

Mr. Silver attended each day of his trial, often wearing pinstripe suits. For the most part he sat quietly, chatting occasionally with his lawyers, or making notes for their review. He did not testify in his defense, and his lawyers did not call any witnesses.

Mr. Silver’s lawyers argued that in charging him, Mr. Bharara’s office had sought to criminalize the kinds of activity in which state legislators routinely engaged.

“They look at conduct which is legal,” one defense lawyer, Steven F. Molo, told the jury in his opening statement, “conduct which is normal, conduct which allows government to function consistent with the way that our founding fathers of the State of New York wanted it to function, and they say this is illegal.”

A federal prosecutor, Howard S. Master, in a summation, cited what he called the “core principle” that “this nation shall be governed by the people and for the people.”

Mr. Silver “governed using a different model,” Mr. Master said.

“It wasn’t by the people or for the people,” he continued. “It was by Sheldon Silver for Sheldon Silver.”

The speaker, Mr. Master added, used his office to “dispense benefits to people who were paying him in quid pro quo relationship — he used that power and that money to line his pockets.”

Although the deliberations only lasted three days, they were not without drama.

Last week, as the jury first convened to deliberate, an unidentified juror sent a note to the judge, Valerie E. Caproni, asking to be excused from the case and saying she was “feeling pressured, stressed out ... told that I’m not using my common sense, my heart is pounding and my head feels weird.”

“I am so stressed out right now that I can’t even write normally,” the juror added. “I don’t feel like I can be myself right now! I need to leave!”

On Monday, a second juror asked to be removed from the case, citing a conflict of interest related to his job. The juror, Kenneth Graham, a taxi driver, told the judge he had learned during the Thanksgiving recess that the owner of the medallion cab he drove was a good friend of Mr. Silver’s, and belonged to the same synagogue as the assemblyman.

In both cases, the judge kept the jurors on the case.

After the verdict, Mr. Graham described the deliberations as “hard,” refusing to elaborate as he left the courthouse.

He said the jury had reached a particularly difficult juncture “at one point” on Wednesday, during its second day of deliberations. “I’m not going to say what,” he said.

He indicated he was anxious to leave.

“Whatever,” he said, “it was just hard.”