DAYS BEFORE the official launch of his reelection bid, D.C. Mayor Vincent C. Gray (D) offered his first public apology for the events that sullied his 2010 campaign. Good that the mayor finally recognized the need for contrition for the corruption that accompanied his election to office. But words of regret must be only a first step. They cannot substitute for a full accounting of what he did and knew four years ago.

“Frankly, the things that happened in my campaign, you know, they were painful, they were embarrassing to me,” Mr. Gray told WUSA-TV (Channel 9) in an interview that aired Wednesday . “There were things that I wish hadn’t happened, and I’m very sorry those things happened.” Four people associated with Mr. Gray’s campaign, including longtime friends, pleaded guilty to felonies in an ongoing federal probe that uncovered a “shadow campaign” of illegal corporate money benefiting Mr. Gray.

Mr. Gray reiterated a previous claim that he “ didn’t do anything” and said he couldn’t apologize “for what other people did.” He denied giving cash to Sulaimon Brown, the fringe mayoral candidate whose claims of a quid pro quo led to the federal investigation. He said Jeffrey E. Thompson, the city contractor alleged (but not charged) to have financed the shadow campaign, never asked him for anything.

Many questions remain.

When did Mr. Gray first learn of the secret and illegal shadow campaign? Is it correct, as a former campaign worker has alleged, that questions were raised directly with Mr. Gray in the summer of 2010 about the source of funding for field operations directed by Vernon Hawkins, one of Mr. Gray’s confidants who has pleaded guilty to a felony?

What was the purpose of a meeting in the spring of 2010 between Mr. Gray and Mr. Thompson at the apartment of Jeanne Clarke Harris, who has pleaded guilty to helping disguise the source of the illegal funds? What did the two men discuss when they met again after the mayor’s election? Did the topic of Mr. Thompson’s lucrative city contract come up? A few months after Mr. Gray became mayor, the city had a change of thinking about paying a multimillion-dollar settlement (now under scrutiny by federal investigators) to the health-care firm owned by Mr. Thompson.

Mr. Gray has been unwilling to entertain these questions. He has not stood before the media, as New Jersey Gov. Chris Christie (R) did Thursday, to answer every question put to him. He has declined requests to meet with investigators from the U.S. Attorney’s Office. Mr Gray may, as his campaign manager told The Post’s Mike DeBonis, need to “turn the page” on 2010. But voters need to know what is written on that page.