Outgoing District of Columbia Mayor Vincent Gray rejected a proposed plea bargain offered by federal prosecutors investigating financial irregularity in his 2010 mayoral campaign, according to a published report. 

The Washington Post, citing a person with knowledge of the talks, reported that a deputy to U.S. Attorney Ronald Machen offered the deal in a meeting with Gray's attorney in September. According to the offer, Gray would have pleaded guilty to a single felony count. The paper reported that Gray attorney Robert Bennett told the prosecutor that Gray would not accept any deal requiring him to enter a guilty plea to any charge. 

The Post also reported that since the mayor turned down the proposed deal, federal investigators have re-interviewed several witnesses in the case, including some who have already accepted plea deals. According to the paper, the interviews appear aimed at firming up the prosecution's case before asking a grand jury to return an indictment against Gray. 

Six people have pleaded guilty to federal crimes related to Gray's campaign since 2012. Most of the allegations surround Gray's knowledge of a $653,000 "shadow campaign" on his behalf funded by local businessman Jeffrey Thompson and run by two other close associates of the mayor. Thompson pleaded guilty to two felony charges this past March. 

Gray has repeatedly denied any wrongdoing in connection with his campaign. In an interview with the Post Friday, Gray repeated his denial when the plea bargain possibility was raised, saying "What would I plead to? I don’t know how to put it any other way than that."

Gray defeated incumbent mayor Adrian Fenty in the 2010 Democratic primary, which amounts to a de facto mayoral election in the heavily Democratic District. This past April, two weeks after Thompson's guilty plea, Gray was defeated in the primary by city councilmember Muriel Bowser, who went on to win the general election. 

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