The prominent Boston developer Arthur Winn is pleading guilty to a pair of misdemeanor campaign finance violations, and a development company formerly headed by Winn agreed to pay a $1.5 million fine, in a case that should mark the end of the Dianne Wilkerson saga on Beacon Hill.

US Attorney Carmen Ortiz today announced campaign finance charges against Winn and Winn Columbus Center Limited Partnership, a development firm that had sought to build an $800 million project over the Massachusetts Turnpike in Boston. Ortiz and the Boston office of the FBI alleged that Arthur Winn, Winn Columbus Center LP, and Martin Raffol, a former employee of another Winn subsidiary, had together channeled $150,000 in improper campaign contributions to federal, state, and local candidates.

Arthur Winn is pleading guilty to two misdemeanor campaign finance violations, for reimbursing family members for federal campaign contributions they had made to two Massachusetts congressmen. Together, those illegal contributions totaled $4,500. Under the terms of his plea, prosecutors will recommend that Winn not serve any prison time. Under federal sentencing guidelines, he faces up to six months in prison, and a $100,000 fine.

Winn Columbus Center LP, a shell corporation that sought to construct the failed Columbus Center development on Boston’s Back Bay-South End line, has agreed to pay a $1.5 million fine. Raffol pleaded guilty to federal campaign finance violations last year. He has not yet been sentenced. He was believed to be cooperating with the FBI’s investigation into Winn.

The FBI’s interest in Winn sprang from its investigation into Wilkerson, the former state senator who was convicted of taking $23,500 in bribes earlier this year. As CommonWealth wrote earlier this year, undercover FBI agents investigating Wilkerson attended a fundraiser at a hotel developed by Winn. At that fundraiser, Wilkerson received campaign contributions from a number of vendors working for Winn’s affordable housing division. Some of those vendors were later reimbursed for their contributions through inflated work invoices.

Wilkerson was an ardent supporter of Columbus Center, a project that sought special tax treatment and development assistance from federal, state and local authorities. In particular, Wilkerson championed a $10 million state grant that the Patrick administration eventually rescinded. Winn also gave Wilkerson $10,000 to help settle her personal debts.

The FBI, already investigating Wilkerson for taking bribes related to development, took a run at Winn, a prolific political fundraiser whose companies benefited from public subsidies. But they’ve never alleged, let alone levied charges, related to any bribery by Arthur Winn or any other employee of Winn’s development companies. Today’s pleas put an end to that investigation.

“The whole area of political contributions is rife with hypocricy,” Winn’s attorney, Robert Popeo, told CommonWealth. “It’s possible to legally make campaign contributions much larger than the contributions Winn is pleading guilty to.” Popeo said that, while Winn is admitting he broke the law, “You shouldn’t prosecute people for doing something they could do legally. There’s no reason to violate this law, if you’re well informed.”