A former campaign adviser to Mayor Vincent Gray pled guilty Tuesday to lying to federal investigators and bribing a witness to leave town.

Vernon Hawkins, 74, has been accused of running a $653,800 “shadow campaign” that helped Gray win the city’s mayoral race in 2010. Hawkins is the first person charged in the investigation with ties to both Gray and businessman Jeffrey E. Thompson, who allegedly supplied the cash.

Hawkins faces a $250,000 and a maximum of five years in prison. If he cooperates with investigators, that sentence could be decreased to less than 16 months.

A second Gray campaign official pled guilty last year to lying to investigators and paying a candidate to verbally attack Gray’s opponent, then incumbent Mayor Adrian Fenty.

Gray has claimed he did not know about the fund. D.C. Council members David Catania, Muriel Bowser and Mary Cheh have each called for Gray’s resignation over the last two years.

“If somebody comes into office as the beneficiary of the biggest election fraud in the history of the District of Columbia government, then holding that office is untenable. In other words, you should submit yourself to the voters again in a fair, honest election,” Cheh told WTOP Monday.