Updated

For the second time in three days, a former campaign staffer to District of Columbia Mayor Vincent Gray has pleaded guilty to a federal offense arising from Gray's 2010 mayoral bid.

Howard Brooks pleaded guilty Thursday to lying to the FBI about payments he made to another mayoral candidate using Gray campaign funds. On Tuesday, former Gray aide Thomas Gore pleaded guilty to making some of the same payments and shredding records of them.

Authorities said the cases revealed that the Gray campaign engaged in dirty politics.

"Today's guilty plea further reveals the underhanded dealings that tainted the integrity of the 2010 mayoral campaign," U.S. Attorney Ronald Machen said in a statement.

What remains unclear is whether Gray participated in or even knew about the criminal activity. While Gray has suffered politically from the scandal, he has not been implicated in any crimes. He has insisted previously during a long-running federal probe that he knew nothing about the potential misdeeds committed by staffers.

The most serious offenses that arose from the cases against Gore and Brooks occurred after Gray took office and involved attempts to conceal the Gray campaign's schemes. Gore pleaded guilty to shredding records of payments made with Gray campaign funds to Sulaimon Brown, a minor mayoral candidate. And Brooks admitted lying to the FBI about his involvement in giving Brown the money.

Brown was paid so that he could continue making negative comments about then-mayor Adrian Fenty on the campaign trail, authorities said. According to court documents, Gore and Brooks conspired with another, unnamed Gray campaign staffer to funnel at least $2,810 in cash and money orders to Brown. The effort was funded with excessive or unattributed cash contributions to the Gray campaign.

Court documents indicate that Brooks was "instructed" to pay Brown, but it's not clear who instructed him. Brooks' attorney, Glenn Ivey, said after the hearing that the scheme to pay Brown was not his client's idea.

The third campaign staffer has not yet been charged. Brown has alleged that he received money from Brooks and Lorraine Green, Gray's campaign chairwoman and a close personal friend of Brooks. Green has acknowledged meeting Brown and speaking with him by phone on several occasions, but she denied giving him money or promising him a job in the Gray administration.

Green's attorney did not return a message seeking comment Thursday.

Administration officials have maintained Brown was only promised an interview, but Brown was ultimately appointed without an interview to a $110,000-a-year position. He was fired after less than a month, and went public with his allegations after that.

Gray defeated Fenty by 10 percentage points in the 2010 Democratic primary, harnessing widespread dissatisfaction with a mayor perceived by many as aloof. Gray ran on a platform of restoring integrity to government, but his administration became mired in scandal shortly after he took office.

The payments to Brown are just one aspect of the federal probe. In March, investigators raided the home and offices of Jeffrey Thompson, a well-connected government contractor who was a major contributor to Gray's campaign. The U.S. Attorney's Office has not commented on the raid.

On Thursday, Brooks acknowledged making $2,000 in contributions to the Gray campaign in his own name with money that was not his. The source of the funds was unclear.

Brooks has cooperated extensively with federal investigators and wore a wire during a meeting with Gore last fall. Under federal sentencing guidelines, Brooks would receive a maximum of 6 months in prison and could receive probation. Ivey said he thought probation was appropriate. No sentencing date was scheduled.

"Although Mr. Brooks' conduct was egregious, he deserves some credit for owning up to his mistakes and eventually telling the truth," Machen said. "We urge others to do the same as we continue our efforts to get to the bottom of what happened during the 2010 election."

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