An undercover FBI agent met Jackson as part of the Chow investigation, and Jackson invited him to contribute to Yee, who was trying to retire a campaign debt and raise funds for his campaign for California secretary of state.

The agent's introduction to Yee led to a long series of contacts involving other undercover agents. Yee and Jackson were indicted and arrested in March 2014 after they negotiated bribes to support legislation and payments for a variety of favors, including an official state Senate proclamation congratulating Chow's Chee Kung Tong organization.

Yee told Breyer that "nothing that I will ever do will take away the pain that I’ve caused to my family, friends, supporters and the institution that I represent.”

Nevertheless, Yee said, "I hope that in your sentencing of me that you look at the entire life and not just these crimes that I’ve committed. In the 67 years of my life, I have devoted much of it to the work for the community of people here in San Francisco and the state of California."

"Senator Yee has taken responsibility, has led a good life, has made mistakes, has admitted his mistakes, and he shouldn’t be sort of overpunished because he happens to be a public official," said defense attorney James Lassart. "It should not be an overarching crushing of this man."

But Breyer blasted Yee for abusing the public's trust and offering his vote for sale.

"In the court’s view, this is a very serious violation of trust," Breyer said. "Votes are not for sale, positions are not for sale, and your conduct, and it’s on hours and hours of tape indicating that it was for sale, is a violation of trust. "

Breyer also fined Yee $20,000. Yee, who had served on the San Francisco school board and Board of Supervisors before being elected to both houses of the state Legislature, must surrender to begin his sentence in 30 days.

Separately, Breyer sentenced Jackson to nine years in prison, eliciting quiet sobs from a supporter in the court's audience. Prosecutors had requested a 10-year sentence, the maximum allowed under Jackson's plea agreement. Breyer said he considered it, given the former political consultant and San Francisco school board president's conduct was "akin to being a one-person crime wave."

"The scope of your criminal involvement was enormous," Breyer said, adding that Jackson's crimes -- including gun and drug trafficking and facilitating illegal pay-to-play campaign donations for Yee -- is "extremely disturbing."

Jackson made a short statement to the court, telling Breyer that that he takes full responsibility for his actions.

"I know I could have walked away," he said, "and I should have walked away."

Federal prosecutors, who portrayed Yee as a cynical grafter, had asked for a sentence of eight years in prison and a $25,000 fine, which would have been beyond federal sentencing guidelines.

Yee's defense lawyer had sought a sentence of no more than five years and three months -- but had also suggested Yee do no prison time because of his wife's condition.

Jackson and Yee were also implicated in a scheme to traffic weapons. Yee and Jackson told the original undercover agent in the case they had contacts who could secure a wide range of arms, including automatic weapons and shoulder-fired missiles.

"We believe that we took a large number of incredibly dangerous firearms off the street and potentially prevented a great deal more from coming to the Bay Area," federal prosecutor William Frentzen told Breyer.

Yee was a noted proponent of stricter gun control during his tenure in the Legislature, a fact an incredulous-soundng Breyer noted during Wednesday's sentencing: