The statistics are certainly on his side: six leak-related prosecutions in Mr Obama's first term, compared with three under all previous presidents combined. It is a record that has heartened security hawks while drawing criticism from advocates for whistle-blowing. But a closer look reveals a surprising conclusion: the crackdown has nothing to do with any directive from the president, even though he is now promoting his record as a political asset.
Instead, it was unplanned, resulting from several leftover investigations from the Bush administration, a proliferation of e-mail and computer audit trails that increasingly can pinpoint reporters' sources, bipartisan support in Congress for a tougher approach, and a push by the director of national intelligence in 2009 that sharpened the system for tracking disclosures.
Even Mr. Obama's attorney general, Eric H. Holder Junior, whose Justice Department has pursued five of the six cases, was surprised by news reports pointing out that the number of cases was unprecedented, colleagues said. He has told associates that he has no desire for leak prosecutions to be his legacy.
"When we took office in January 2009, I don't think bringing a lot of leak cases was high on anyone's agenda," said Matthew Miller, who was director of public affairs at the Justice Department until July. "But then they came up one by one, and without anyone realizing it, we had set a record."
This month Mr Holder directed two United States attorneys to take charge of investigating the latest disclosures, on drone strikes, cyberwar and a foiled airliner plot by Al Qaeda's branch in Yemen. If the inquiries result in still more prosecutions, they will underscore a turn toward a more adversarial stance by the government on news gathering - but one that did not result from a clear policy decision, according to White House and Justice Department officials.
Like most presidents, Mr Obama has been infuriated by some leaks, but aides say he never ordered investigations. Current and former officials said Mr Obama and Mr Holder, who are social friends, have avoided discussing investigations and prosecutions to avoid any appearance of improper White House influence, a charge Democrats lodged against the Bush administration.
Asked whether the White House had a role in the leak cases, a spokesman for the National Security Council, Tommy Vietor, said, "Decisions about leak prosecutions are made by the Department of Justice."
For decades, the Justice Department was where leak complaints from the intelligence agencies went to die. The department's counterespionage section was more interested in finding foreign spies than American blabbermouths, officials said.
Leak cases can also be hard to investigate. When hundreds of officials knew a secret, it was often impossible to find the leaker without a reporter's testimony. But because subpoenas for reporters raised Constitutional concerns about press freedom, they rarely got approved.
Even after the Sept. 11 attacks, the Justice Department under the Bush administration's first attorney general, John Ashcroft, let dozens of referrals from intelligence agencies die out of concern that some leak cases could be impossible to make without subpoenaing reporters. There was also concern that prosecution could harm national security by bringing more attention to the disclosures, said Mark Corallo, his director of public affairs.
That stance began to shift in Mr Bush's second term, when Alberto R. Gonzales took over as attorney general. A Pentagon official pleaded guilty to leaking information to two pro-Israel lobbyists, and the administration got into pitched battles with news outlets, including The New York Times, over disclosures about secret prisons and eavesdropping without warrants.
In addition, the Bush administration assigned at least two cases to hard-charging prosecutors outside the counterespionage section: those of Thomas A. Drake, an N.S.A. official accused of telling The Baltimore Sun about wasteful spending on technology; and of Jeffrey Sterling, a former C.I.A. officer accused of disclosing the agency's efforts against Iran to James Risen, a reporter for The Times, for a book. Both cases were still open at the end of the Bush years.
Changing technology, meanwhile, was making investigations easier. Government officials and reporters were increasingly leaving electronic trails, including e-mails, cellphone records, credit card receipts and computers that tracked everyone who looked at a particular classified document.
Mr. Obama campaigned for the presidency in 2008 championing whistle-blowers who had disclosed government lapses and wrongdoing. But by 2009, in response to complaints from the Congressional intelligence committees about disclosures, a task force created by the Justice Department and the director of national intelligence, Dennis C. Blair, streamlined procedures to follow up on leaks.
Also, Mr Blair said, "we set up a system for tracking and emphasizing security breach investigations, set deadlines and priorities and kept the pressure on."
The scattered bureaucratic background of the six cases appears to support the notion that they were not the result of a top-down policy. Two were handled by the Justice Department's criminal division, while two others were developed by the national security division. A case involving a former C.I.A. officer, John Kiriakou, started with an unrelated inquiry at Guantanamo Bay, Cuba, and ended up as a leak case by accident. And the case against Pfc. Bradley Manning, an Army intelligence analyst accused of delivering huge archives of classified documents to WikiLeaks, was a military prosecution that would most likely have been brought under any administration.
Several current and former Justice Department officials in the Obama administration insisted that neither the White House nor Mr Holder had issued any policy directive calling for more leak prosecutions. Still, Mr Holder approved issuing a subpoena to Mr Risen in the Sterling case, was briefed on all the cases before charges were filed and raised no objections, aides said.
Mr Holder, a former career prosecutor, could have halted any of the cases. But to block a case after years of investigation might anger the prosecutors who are supposed to take it to trial.
Richard Thornburgh, who served as attorney general from 1988 to 1991, said he never quashed a leak case - none were deemed prosecutable during his tenure - but added that it would be unusual to block a case at the last moment.
"Ideally, what you would do in a high-profile case is have some early entry to vitiate the need to have to quash it or deter people from bringing it on the eve of indictment," he said.
Only two of the six cases have concluded: Shamai K Leibowitz, a Hebrew language translator for the F.B.I., quietly pleaded guilty to disclosing classified information and received a 20-month sentence. Mr. Drake's case collapsed; he pleaded guilty to a minor charge and got no jail time. That case was particularly embarrassing for the government: critics call Mr Drake a classic whistle-blower who tried to save taxpayers more than $1 billion.
"If they had it to over again, I suspect the department likely would not bring the Drake case," said Mr. Miller, the Justice Department's former spokesman.
Mr. Corallo, the former top aide to Mr. Ashcroft, faulted the Obama administration for allowing so many leak cases to go forward. "Sometimes the interests of the prosecutor in the field are at odds with the overall health of our republic," Mr. Corallo said, adding that Mr. Holder and his top aides had not been "doing their job, which is to make serious judgments about the overall effects of a leak investigation."
Facing sharp criticism from Senate Republicans this month for refusing to appoint special counsels for the latest leak investigations, Mr. Holder defended himself by pointing again to the prosecution record.
"We have tried more leak cases - brought more leak cases during the course of this administration than any other administration," Mr. Holder told the Senate Judiciary Committee. "I was getting hammered by the left for that only two weeks ago. Now I'm getting hammered by the right for potentially not going after leaks. It makes for an interesting dynamic."