Bill Clinton’s memoir will hit bookstores later this month, but one story you’re not likely to read in its pages involves Clinton’s friendship with Arthur A. Coia. The debonair former president of the Laborers International Union of North America (LIUNA) was one of the Democratic Party’s biggest contributors when Clinton was in office. In the first four years of the Clinton administration alone, LIUNA gave $4.8 million to Democrat candidates and the Democratic Party. Although Clinton had contact with Coia no fewer than 120 times, their association is an awkward memory for the former president given the latter’s ties to organized crime and that of the union he once headed.

In 1986, President Reagan’s Commission on Organized Crime identified LIUNA as one of the “bad four” — the most corrupt unions in the nation — along with the Teamsters, the Hotel Employees and Restaurant Workers, and the International Association of Longshoremen. According to Congressional testimony by the FBI, each of these union’s presidents at the time had been “handpicked by La Cosa Nostra.” Angelo Fosco, who served as LIUNA president from 1975-1993, won reelection while he was under federal indictment for union racketeering — a victory won through “the use of force and threats of violence against potential competitors,” according to the Reagan Crime Commission.

And Coia was no exception. He became secretary treasurer of LIUNA in 1987, the No. 2 job in the union, with the blessings of the Chicago mob, according to Coia’s own admissions in sworn testimony. When Clinton tried to reward Coia for his political contributions by appointing him to a prestigious presidential commission, the Council on Competitiveness, the appointment set off alarm bells at the FBI. In a memo, investigators doing a background check wrote, “Coia is a criminal associate of the New England Patriarca organized crime family.” The bureau also warned the White House that “within the next several weeks” the Department of Justice “will accuse Coia of being a puppet of the LCN (La Cosa Nostra).” Associate Deputy Attorney General David Margolis even tried calling the White House to warn officials not to get too close to the alleged mob-controlled union boss — to no avail.

Although Clinton dropped plans to name Coia to the Council on Competitiveness, he continued to meet with the union leader, exchanged expensive gifts and frequent notes with him, and invited him to travel aboard the presidential aircraft on a trip to Rhode Island. All of this went on while the Justice Department was preparing a racketeering complaint against Coia and his union. On Nov. 4, 1994, the Justice Department’s Organized Crime and Racketeering Section served Coia with a 212-page draft complaint.

“Then something strange happened,” noted the liberal muckraking magazine Washington Monthly at the time. Instead of indicting Coia, the Justice Department worked out a sweetheart deal that allowed Coia to avoid prosecution and keep his job, while a federally appointed investigator pursued lower-level mobsters within the union. Just days before the Justice Department offered the deal, Hillary Clinton traveled to Miami to address the annual LIUNA conference on Feb. 6, 1995, despite warnings from the Justice Department that the trip was ill advised.

The decision not to move forward with its complaint shocked everyone, except perhaps Coia himself. The Justice Department had previously filed racketeering charges in 15 other union cases, taking over the corrupt unions’ operations. But Clinton couldn’t protect his union benefactor forever — especially when Coia himself couldn’t keep his hands out of the union cookie jar. In January 2000, Arthur Coia pled guilty for failing to pay taxes on the purchase of three Ferraris from a Rhode Island car dealer who held a million-dollar leasing agreement with the union. As part of his plea agreement, Coia stepped down as LIUNA president but was allowed to keep his $250,000 yearly salary for life.

If the Clinton administration’s dealings with Arthur Coia and the Laborers Union were an isolated incident, it would be bad enough, but the corrupting nexus between union money and Democratic political power was especially tight during the Clinton years. But the unions’ role in financing Democrats didn’t end when Bill Clinton left office.

This election cycle, unions will spend an estimated $800 million, much of it hidden in the form of salaries for union officials assigned to work on political campaigns, member communications, get-out-the-vote efforts, and other unregulated contributions that go overwhelmingly to elect Democrats. But don’t expect to read about it on the front page of the New York Times or in Clinton’s memoir.