The sudden fall of a man who once stood at the pinnacle of political power in New York is expected to reach a dramatic climax Tuesday afternoon with the sentencing of ex-Assembly Speaker Sheldon Silver for using his power to line his pockets with $4 million in law firm referral fees.

U.S. Attorney Preet Bharara’s office has urged U.S. District Judge Valerie Caproni in Manhattan to make an example of Silver, casting him as a chief architect of corruption in Albany and calling for at least 14 years in prison — the highest federal prison term ever for a New York legislator.

“Silver’s crimes corrupted the institution that he led for more than 20 years,” prosecutors said in a filing with the judge last month. “As a fixture in the legislative leadership, an entire generation of New York legislators served in an institution framed by his corrupt example. His crimes struck at the core of democratic governance.”

But Silver, 72, and his lawyers have asked Caproni to show leniency toward the disgraced ex-speaker in recognition of his years of public service and the good things he did, instead of using a harsh sentence to send a message in Bharara’s campaign for ethics in New York politics.

“Just because a person acts positively on some or many occasions doesn’t mean that they don’t act wrongfully on other occasions,” Silver wrote in a letter to Caproni. “I understand that, truly. But I respectfully ask Your Honor to examine the ‘good things’ I have tried to do as a public servant as an individual.”

Silver was convicted in December of doing legislative favors for an asbestos researcher and two developers who funneled law firm referral fees to him. Silver and former Senate Majority Leader Dean Skelos, also convicted in December and scheduled to be sentenced next week, are the two biggest Bharara has taken down in his clean-up-Albany campaign.

While Bharara’s anti-corruption investigations remain active, with ongoing probes targeting aides to Gov. Andrew M. Cuomo and Mayor Bill deBlasio’s fundraising, Bharara and others have been critical of the lack of legislation in Albany to tighten up ethics laws.

The federal probation office has recommended a 10-year prison sentence, but Bharara’s prosecutors have urged Caproni to exceed the previous high for a New York legislator — 14 years imposed on former Assemb. William Boyland in Brooklyn last year for two separate bribery schemes and submitting phony expense vouchers.

Silver, the government says, had a leadership role in the Assembly unlike Boyland, had an even higher recommended range than Boyland of at least 22 years under federal sentencing guidelines, and like Boyland went to trial instead of pleading guilty.

Prosecutors have also urged the judge to impose a hefty fine of at least $1 million, in addition to forfeiture of all the fruits of the crime, so that his benefits from his $73,000 annual state pension are limited.

In addition to his conviction for using his public office in return for legal fees, Silver was also damaged after trial when Caproni ordered the release of government filings alleging he engaged in extramarital affairs with a lobbyist and a woman he helped get a state job.

Caproni, a former prosecutor and general counsel at the FBI who was named to the federal bench in 2013, said that even though the evidence of affairs hadn’t been admitted at trial, it was relevant to her sentencing decision because it reflected other examples of Silver’s misuse of public office.

Silver’s sentencing submission included dozens of letters of support from such luminaries as former New York City Mayor David Dinkins. It said Silver has arranged with the Fortune Society, a group that aids convicts with re-entry programs, to work as an employment services counselor if Caproni orders community service.

Silver has also revealed that he has prostate cancer, currently in remission.

“It terrifies me that his father and brother both died of the same kind of cancer Shelly was diagnosed with,” his wife of 49 years, Rosa, wrote to the judge. “I am afraid he will be sick and, even worse, alone.”