In fact, Mr. Drake initially drew the attention of investigators because the government believed he might have been a source for the December 2005 article in The Times that revealed the wiretapping program.

Describing for the first time the scale of the Bush administration’s hunt for the sources of The Times article, former officials say 5 prosecutors and 25 F.B.I. agents were assigned to the case. The homes of three other security agency employees and a Congressional aide were searched before investigators raided Mr. Drake’s suburban house in November 2007. By then, a series of articles by Siobhan Gorman in The Baltimore Sun had quoted N.S.A. insiders about the agency’s billion-dollar struggles to remake its lagging technology, and panicky intelligence bosses spoke of a “culture of leaking.”

Though the inquiries began under President Bush, it has fallen to Mr. Obama and his attorney general, Eric H. Holder Jr., to decide whether to prosecute. They have shown no hesitation, even though Mr. Drake is not accused of disclosing the N.S.A.’s most contentious program, that of eavesdropping without warrants.

The Drake case epitomizes the politically charged debate over secrecy and democracy in a capital where the watchdog press is an institution even older than the spy bureaucracy, and where every White House makes its own calculated disclosures of classified information to reporters.

Steven Aftergood, head of the project on government secrecy at the Federation of American Scientists, who has long tracked the uneasy commerce in secrets between government officials and the press, said Mr. Drake might have fallen afoul of a bipartisan sense in recent years that leaks have gotten out of hand and need to be deterred. By several accounts, Mr. Obama has been outraged by some leaks, too.

“I think this administration, like every other administration, is driven to distraction by leaking,” Mr. Aftergood said. “And Congress wants a few scalps, too. On a bipartisan basis, they want these prosecutions to proceed.”