D.C. Mayor Vincent Gray files paperwork to run for reelection at the D.C. Board of Elections in Washington, Monday, Dec. 2, 2013. (Cliff Owen/AP)

Mayor Vincent C. Gray, in his first full day as a candidate in more than three years, faced a new round of questions Tuesday about his previous campaign as he sought to keep the public focused on his mayoral record and his plans for a second term.

“I want to talk about the future of this city,” Gray said, repeating various permutations of that phrase a half-dozen times during an occasionally fiery news conference.

The event, held atop an unfinished luxury apartment building in the gentrifying Shaw neighborhood, was intended to highlight Gray’s record on economic development. A nearly hour-long presentation touched on projects ranging from a “culinary incubator” to technology start-ups to the pair of Wal-Marts, the city’s first, set to open Wednesday.

Gray (D) was less voluble when addressing questions relating to his 2010 campaign, which remains the subject of a federal corruption investigation, according to a spokesman for U.S. Attorney Ronald C. Machen Jr.

Gray has denied wrongdoing in general terms since allegations were first raised in early 2011. But he has refused to discuss many specific matters, including details of his dealings with Jeffrey E. Thompson, the former city contractor implicated in the funding of an illicit “shadow campaign” on Gray’s behalf, or his thoughts on the guilty pleas entered by four campaign associates, some of them close friends.

Gray gave no indication Tuesday that he would go beyond his previous statements.

“I’ve said what I’ve said, I’ve said it repeatedly, and, you know what? There’s no end to that,” he declared. “I probably could have avoided all of this by not even getting into this race at this stage. . . . 2010 is now getting ready to be four years ago, okay? And I want to talk about what happens going forward in 2014.”

The mayor may struggle to maintain that stance on the campaign trail and through its grinding schedule of candidate forums and media interviews.

Andy Shallal, a prominent restaurateur who launched a mayoral bid last month, said he will press Gray to say more. “People want to know, were you aware of this and did you do something about it?”

Among the questions Gray declined to address Tuesday was whether he has personally cooperated with the federal investigation, which was touched off by revelations that a minor mayoral candidate in 2010, Sulaimon Brown, had received secret cash payoffs from Gray campaign operatives in exchange for verbal attacks on incumbent Adrian M. Fenty, Gray’s top rival in the Democratic primary.

The inquiry later expanded to encompass the shadow campaign, which included illegal, unreported expenditures to help Gray win and was allegedly orchestrated by Thompson. Thompson has not been charged with a crime but has been identified by people familiar with the investigation as the unnamed co-conspirator implicated in several of the prosecutions.

Robert S. Bennett, Gray’s personal attorney, declined to comment Tuesday on Gray’s interactions with investigators. A spokesman for Machen declined to comment on the matter.

When the Brown allegations were first detailed in The Washington Post, Gray called an unusual Sunday evening news conference to deny allegations of a quid pro quo, saying he had promised Brown only a job interview and had no knowledge of cash payments. But when prosecutions of two campaign aides took place more than a year later, Gray kept mum.

He has been even more reticent to discuss Thompson or the shadow campaign. After the full scope of the operation was aired in court documents filed in July 2012, Gray said only, “This was not the campaign we intended to run.”

He also has not commented on a January 2011 meeting in his John A. Wilson Building office with Jeanne Clarke Harris, a public relations consultant who admitted in court that she helped coordinate the shadow campaign. Nor has he detailed his understanding of Thompson’s alleged campaign activities — arranged, The Post has reported, during a spring 2010 meeting in Harris’s apartment.

When operative Vernon E. Hawkins pleaded guilty in August to lying to federal investigators, Gray again had little to say about someone who had been one of his most trusted political hands.

During the question-and-answer session Tuesday, Gray was unusually combative, sparring with some reporters, cutting off others and exploding at the suggestion, from a Washington City Paper writer, that he might not be personally responsible for all of the economic development progress he sought to highlight.

“Excuse me for saying this, you are just plain wrong,” he said before calling on reporters to be “boosters for their city” rather than “sit there and try to pick a hole in anything they get their hands on.”

Gray picked up his petitions Monday, four months ahead of the primary, and he has said he won’t be launching a formal campaign until after New Year’s Day. That puts his reelection campaign on an even tighter timeline than the 2010 effort, which was launched 5 1 / 2 months ahead of the primary.

Gray said he would be more “directly involved” in his campaign than in 2010, when he was serving as D.C. Council chairman.

“The others will have to say what they’re going to do; people are going to look at my record,” he said. “If I were a voter, which I am, that’s exactly what I would look at. I would ask: ‘What have you accomplished, Gray, in the last three years?’ That’s your campaign right there.”

Ann E. Marimow and Nikita Stewart contributed to this report.