The investigation into Vince Gray‘s 2010 mayoral campaign got something else today: a new union angle. Pleading guilty to conspiring to cover up illicit help for Gray’s campaign, former Gray driver Mark Long also admitted to handing off a mysterious package to a pro-Gray union official.

After Gray won the primary, according to Long, Jeanne Clarke Harris told him to drive her to an office building somewhere in Northwest D.C. Harris, who has already pleaded guilty to her own role in covering up former District Medicaid contractor Jeff Thompson‘s illegal shadow campaign to elect Gray, handed Long a package when they reached the building.

Then, according to Long, Harris told him to hand the package to a man on the street. After making the handoff, Long realized that the man was a labor official whose union endorsed Gray, according to court documents.

Neither the official or his organization, which could be one of many unions that backed Gray against Adrian Fenty, are named. The package’s contents also aren’t explained. In Thompson’s own guilty plea, he mentioned spending $10,000 at Gray’s request to sway what has been identified as the Washington Teacher’s Union officer election.

Gray has previously denied committing any crimes during his campaign. With the mayor in China at a tourism conference this week, Gray spokeswoman Doxie McCoy declined to comment on the campaign.

While Long acknowledged the union package in court, the charge he pleaded guilty to relates to his work as Gray’s campaign driver. Instead of being paid by the campaign, Long received a salary from one of Harris’ companies that was used as a funnel for Thompson’s illicit funds. As one part of the scheme, Long claims that he drove Gray to a meeting where he unsuccessfully tried to convince mayoral rival Leo Alexander to leave the race.

Long’s statement of offense describes him as a key link between Gray and Thompson. Thompson would call Long on his phone to speak to Gray, according to the statement of offense, and Long collected campaign contributions at Thompson’s office.

Long also says he drove Gray to a meeting at Harris’ apartment where the mayor met with Thompson and Harris. In Thompson’s own court records, he described a meeting there where he said Gray allegedly presented Thompson with a budget requesting more money for the shadow campaign.

As part of his plea, Long agreed to cooperate with investigators.

Photo by Darrow Montgomery