A former correction officer and union president is expected to plead guilty Friday to charges in connection with the investigation of illegal contributions to the congressional campaign of House Speaker Christopher Donovan, D-Meriden.

David Moffa, 52, of Middlebury, the former president of the American Federation of State, County and Municipal Employees, Local 387, is listed on a court docket as scheduled to change his not-guilty plea in U.S. District Court in New Haven. He was one of six defendants indicted in July.

The indictment described Moffa and two smoke shop owners meeting in Waterbury to talk about proposed legislation that could impose fees or taxes on the roll-your-own cigarette business. Federal authorities allege the meeting was part of a conspiracy to kill the bill.

Moffa, according to the indictment, told them at the first meeting he had a friend, another former correction officer and union activist, Ray Soucy, who could put them in touch with Donovan. The owners, later joined by FBI agents posing as businessmen, donated $27,500 to the campaign.

Donovan has not been charged or accused of knowing about the scheme, but the investigation derailed his campaign. He lost a primary in August.

Soucy, who cooperated with investigators before the investigation became public, pleaded guilty in July.

Others charged in the case include Donovan’s former campaign manager and finance chief.