AYEAR has passed since U.S. Attorney Ronald C. Machen Jr. made the startling disclosure that D.C.’s race for mayor in 2010 had been “corrupted by a massive infusion of cash that was illegally concealed” from voters. The revelation prompted obvious questions about what Mayor Vincent C. Gray (D) — whose campaign benefited from a prominent businessman’s unreported contributions — knew, and what he did or didn’t do.

A year later, questions remain — and new ones have emerged.

The latest concern is a recently disclosed meeting in the spring of 2010 between Mr. Gray and Jeffrey E. Thompson, the city contractor who is alleged to have funneled more than $650,000 in unreported money to a shadow campaign that aided Mr. Gray in his successful primary challenge to then-Mayor Adrian M. Fenty (D). A profile by The Post’s Nikita Stewart of Mr. Thompson and his outsize influence on District government cited a source who said that Mr. Thompson promised to give Mr. Gray’s campaign financial support but did not want to do so publicly for fear of angering the incumbent mayor and possibly endangering his company’s lucrative contracts. “It was supposed to be a loan,” the source said, to be reported after the election. The meeting took place at the apartment of Jeanne Clarke Harris, an associate of Mr. Thompson and supporter of Mr. Gray who has pleaded guilty to helping to orchestrate the illegal campaign. Mr. Thompson has not been charged; a person close to the mayor disputed that a loan or illegal contributions were discussed.

What exactly did the men discuss at the meeting, from which, according to Ms. Stewart’s sources, others had been excused? Prosecutors have not alleged that Mr. Gray had knowledge of the “shadow campaign,” but they have said it was “coordinated” with members of his campaign. Campaign materials purchased with the illegal money — yard signs, T-shirts, umbrellas, banners, stickers, posters and more — were delivered to Mr. Gray’s headquarters. Was he unaware of this, even though his late entry into the race had prompted considerable discussion about whether he could raise sufficient funds? Mr. Gray takes pride in his reputation of being able to get into the weeds of public policy and finance.

Soon after the election, Mr. Thompson was said to have met with Mr. Gray, advising him about the budget and his cabinet. Mr. Gray’s administration successfully pushed to increase reimbursement rates to the managed health-care company owned by Mr. Thompson that had a $322 miillion contract with the city. It was a reversal of the hard stance taken by Mr. Fenty’s administration, and it raised eyebrows, particularly since the firm had earlier been accused of overcharging, eventually agreeing to a settlement with the city.

Mr. Gray’s continued silence — even in the face of disturbing new details — is troubling and unacceptable. The obligation of the mayor to level with the people he serves isn’t erased by advice he gets from his private attorney or the timetable of federal prosecutors.