Mayor Vincent Gray at February’s One City Citizen Summit. (Marvin Joseph/The Washington Post)

Federal prosecutors have charged a top aide to Gray’s 2010 mayoral campaign, Thomas W. Gore, with destroying evidence and giving campaign contributions under false pretenses. The charges — filed by criminal information, a likely prelude to a guilty plea — are the first filed in an investigation touched off more than a year ago by the explosive allegations of minor mayoral candidate Sulaimon Brown.

And unless U.S. Attorney Ronald C. Machen Jr. stands up in the coming days to say otherwise, it is safe to assume the federal investigation will continue, and news and speculation on its course is certain to consume the District political scene in the coming weeks and months.

The Gore charges, which include felony obstruction of justice, are serious and make it eminently clear that the federal probe into District campaign matters is for real. They come as the allegations have expanded from a scorned candidate’s cash payoffs to an off-the-books “shadow campaign.”

And it will be difficult for Gray (D), who has previously denied any wrongdoing, to brush off the news as the doings of a rogue operative: Gore is a longtime friend and one of Gray’s most loyal campaign lieutenants. While his recent title was assistant treasurer, campaign sources have told The Post that Gore was the main aide in charge of the 2010 coffers. He had also served as treasurer for Gray’s two previous D.C. Council runs, in 2004 and 2006.

With a plea deal likely to hinge on Gore’s cooperation, prosecutors have secured a set of eyes and ears in the very center of the Gray campaign. Should they wish to expand their probe — to campaign chairwoman Lorraine A. Green or consultant Howard L. Brooks, both named by Brown in his initial allegations, or perhaps to Gray himself — Gore’s testimony would be a solid foundation to build on.

The immediate pressure on Gray now is to explain what he knew and when he knew about the illegal campaign contributions described in the charging documents, as well as Gore’s alleged destruction of evidence — which is said to have come on or around the same day The Post first publicized Brown’s claims.

Gray’s office is referring all questions to his personal lawyer, Robert S. Bennett. He declined to comment to the Post’s Del Quentin Wilber.