Mayor Vincent C. Gray portrayed himself as an unwitting victim of trusted but corrupt campaign deputies in a radio interview Friday, continuing to open up about his controversy-racked 2010 run as he nears a decision on seeking a second term.

“You can’t possibly know many of the things going on in your campaign,” Gray (D) said on WAMU-FM’s “The Politics Hour.” “You wish you could, but you didn’t, and I certainly didn’t.”

Gray’s campaign has been under federal investigation since just months after his inauguration in 2011, an inquiry touched off by a former mayoral candidate’s saying that he had received cash payments from the Gray campaign in exchange for criticizing incumbent Adrian M. Fenty (D).

The investigation, which is ongoing, has broadened considerably, revealing a $653,000 “shadow campaign” that is alleged to have been funded by a prominent city contractor.

Four people associated with Gray’s campaign have pleaded guilty to federal felonies, including Thomas W. Gore, who ran the campaign’s day-to-day finances, and Vernon E. Hawkins, a longtime confidant of Gray’s who is said to have directed the “shadow campaign.”

D.C. Mayor Vincent Gray (Sarah L. Voisin/The Washington Post)

Tom Sherwood, a WRC-TV (Channel 4) reporter who co-hosts the program, asked Gray why trusted campaign advisers had felt empowered to break laws on his behalf.

“I can’t answer that, Tom,” Gray said. “That’s probably a question you need to put to them. . . . I didn’t do anything, and it’s very unfortunate that happened because I think we were running a very strong campaign in 2010, and I think we’ve proven over the last two years and 10 months that this was a good decision by the voters.”

Gray sought to compare his campaign’s failings to problems in then-Mayor Anthony A. Williams’s 2002 reelection effort, when campaign workers, paid to circulate ballot petitions, were found to have forged hundreds of signatures.

Williams (D) failed to qualify for the primary ballot, and his campaign was assessed unprecedented fines. No criminal charges were brought, however, and Williams, who mounted a successful write-in effort, was not directly implicated in wrongdoing.

Gray acknowledged, as he has previously, his dealings with Jeffrey E. Thompson, the former city contractor said to be the source of the secret funding. A “prolific fundraiser,” Thompson never asked him for favors in return for his financial support, Gray said.

“People support people’s campaigns because they don’t like the current administration for whatever the reason may be,” he said. “There is absolutely nothing unusual about it.”

William Miller, a spokesman for U.S. Attorney Ronald C. Machen Jr., said the office had no comment on Gray's remarks.

The comments came a week before ballot petitions will be made available for the April 1 city primaries; Gray would have to collect the signatures of at least 2,000 registered Democratic voters by Jan. 2.

On Monday evening, Gray told a private gathering of supporters he did not consider the petition pickup date to be a hard deadline for his reelection decision, according to attendees, who spoke on the condition of anonymity because of the private nature of the meeting.

On Friday, host Kojo Nnamdi pressed Gray during the radio interview on whether the mayor would feel compelled to give a fuller accounting of what he knew about wrongdoing in the 2010 campaign should he pursue another term.

“There may be questions I can’t answer because I don’t know the answer, but I’ve tried to be clear about that fact that I didn’t do anything,” Gray said. “And I’m not sure what else to say. I’m sure the first 10 questions will lead to 10 more questions, will lead to 10 more questions. When is somebody satisfied?”