WASHINGTON — Few presidential candidates enjoyed better press than Barack Obama in 2008. He reciprocated by promising unprecedented “openness in government” and a new era of transparency.

He has fallen far short of the promise. This administration has prosecuted more whistle-blowers for leaks and gone after more journalists than any of its predecessors.

In a report last year, Leonard Downie, the former executive editor of The Washington Post, said the administration’s efforts to crack down on information seeping to journalists is “the most aggressive” since President Richard Nixon was in office.

The issue was crystallized anew last week when the Supreme Court refused to hear an appeal from New York Times reporter James Risen, who has been ordered to testify in the trial of Jeffrey Sterling, a former CIA official. Sterling is charged with giving Risen classified information about an attempt to sabotage Iran’s nuclear program. The Justice Department has relentlessly pursued Risen, and he could face jail time for failing to comply with the subpoena.

Why has this once-media-friendly administration turned neo-Nixonian? Insiders say it’s the pressure of the powerful national security apparatus and the fear among Obama aides that the president could face the wrath of the intelligence community if he fails to act tough.

The CIA and others invariably contend that leaks imperil the nation. Sometimes they may be right: There’s no defense of a 1942 Chicago Tribune article revealing that the United States had broken the Japanese code. Fortunately, no harm was done. The Tribune apparently didn’t have readers in Tokyo.

More often, clampdowns are intended to cover embarrassments. In 1971, under the guise of protecting U.S. security, the government went to extraordinary efforts to try to block publication of the Pentagon Papers, an internal review of the Vietnam War. The suppression attempt was unsuccessful. In any case, the flaws of the war already were clear to friends and foes alike.

Similar claims about protecting national security are being made about Sterling, who proclaims his innocence. Yet there is evidence the U.S. efforts to sabotage Iran’s nuclear program were botched, and it seems likely the Iranians were aware of the operation.

In the U.S., the news media has considerable protections when it comes to censorship or libel, but they don’t apply to news gathering. Starting with a 1972 decision – handed down 12 days before the Watergate break-in – courts have held that the media have no automatic privilege to protect the identity of a source.

There were further setbacks for journalists a decade ago, when a special prosecutor investigated a leak that revealed the identity of a covert CIA operative, Valerie Plame.

That was a worst-case scenario for the media: a national security issue in which reporters were the only source of information. And the media conflated anonymous sources – who want to be protected for political or personal reasons – with confidential informants, who could be endangered personally or politically if identified.

Some in the media say the answer is a federal shield law that protects a reporter’s right not to divulge sources. Yet that would raise complicated questions about who would be covered, and any measure that could pass Congress would exclude national-security matters, the area in which most controversies arise.

Even Judge David Tatel of the U.S. Court of Appeals, who is sympathetic to the news media’s case, has doubts about such a measure. What if, Tatel asks, nuclear secrets were illegally leaked to a blogger who then posted the information on her website? Would the blogger be entitled to refuse to testify about her sources?

Thus, on the federal level, much depends on an administration’s attitude. Since President Nixon, most have taken a comparatively benign posture. (The Plame case was pressed by a special prosecutor.) The Obama administration has pursued more journalists, secretly looking at phone records and credit-card transactions and surreptitiously tracking their movements.

A federal judge dismissed the proceedings against Risen, but the Obama administration successfully appealed the decision.

Attorney General Eric Holder has vowed in private meetings and some public pronouncements to change this approach. With the decision by the Supreme Court last week, the Risen case offers the opportunity to do so.

The best bet is the government won’t drop the case or prosecute Risen; it will simply decline to call him in the Sterling case. That would provide little clarity.

— The Washington Post News Service with Bloomberg News