HERE’S A STORY that we’ve heard before: The White House is suspected of leaking sensitive national security information to reporters for nakedly political reasons. The Justice Department has opened a criminal investigation, but some in Congress aren’t satisfied. They demand that an independent counsel be empowered to follow the evidence wherever it leads.

The last time an issue like this came up, some Democrats had strong views. Rep. Nancy Pelosi argued that the possibility that the leak came from senior White House officials created a conflict of interest for the attorney general and his staff that could be resolved only by the appointment of an outside counsel. Then Sens. Hillary Rodham Clinton and Joseph R. Biden Jr. agreed: “I think it would be very difficult for the attorney general to oversee such an investigation,” said Ms. Clinton.

Then, of course, the Democrats were talking about the George W. Bush administration’s leak of the name of CIA employee Valerie Plame, whose husband’s attacks on the case for the Iraq war had become a liberal cause celebre. Now, following stories containing disclosures about a cyber­attack against Iran and an al-Qaeda double agent, those same Democrats are happy to leave the investigating to the two federal prosecutors named by Attorney General Eric H. Holder Jr. last week — even though one of the stories, which portrayed President Obama in a favorable light, was sourced in part to unnamed “members of the president’s national security team.”

In 2003, we were initially sympathetic to the Democrats’ position. We came to regret that view as special counsel Patrick Fitzgerald pursued a lengthy, costly and ultimately counterproductive investigation in which several reporters were forced to disclose confidential sources, a New York Times reporter was jailed for 85 days while refusing to do so, a senior White House official was prosecuted for perjury — and no one, including the primary source of the original leak, was sanctioned for that disclosure.

Whether undertaken by Justice’s prosecutors or an independent counsel, the current investigation should, and almost certainly will, lead to a similar dead end — which is one reason we believe it should not have been begun at all. As in previous cases, including the six mostly unsuccessful leak prosecutions so far launched by the Obama administration, it’s doubtful that any law was broken. Disclosing classified information is not by itself a crime, and courts have found that under the flawed 1917 espionage statute used in such cases, prosecutors must show that a leak was intended to harm U.S. security — an appropriately high bar.

Last week Mr. Obama indignantly denied that “my White House would purposefully release classified national security information.” But the president has authority to declassify and disclose such information and did so this year when he spoke about the use of drones to target al-Qaeda operatives. In general, the more that can be made public about a president’s decision-making — whether it is in selecting terrorists for drone strikes or ordering a cyberattack — the better the public is served. Whatever their impact on his reelection prospects, the recent stories about Mr. Obama’s national security decisions were illuminating about critical areas of policymaking. They deserve more airing and debate, not a criminal investigation.

Did top presidential aides respond to reporters’ inquiries by describing situation room meetings and other secret deliberations in an attempt to buff their boss’s image? That wouldn’t surprise us. If Mr. Obama’s opponents believe it to be true and they’re convinced that U.S. interests were harmed, they are free to make that case to the public, as they are doing. But the attempt to criminalize such leaks is misguided and will do more harm than good. Elevating the investigation from the appointed prosecutors to an independent counsel would only compound the damage.