“His supporters say he may have violated the law, but it can be forgiven,” said Richard A. Clarke, a former White House counterterrorism adviser who served on the panel. “I don’t think it can be. In any outcome here, he’s going to serve time. The only question here is how much.”

As the debate plays out, Mr. Snowden watches from refuge in Moscow, where he fled last year after turning over classified documents to journalists from The Guardian and The Washington Post. Even after a lengthy interview published by The Post last month, little is known of his current life beyond his self-description as an “inside cat” who survives on ramen noodles and entertains sympathetic visitors but does not read the books they bring him.

Mr. Snowden claimed vindication last month after a judge ruled against the legality of a telephone metadata collection program detailed in the documents he disclosed. Another judge took the opposite position, but the conflict suggests that the matter is not as cut-and-dried as the government asserts, Mr. Snowden’s advocates said. The White House panel found “persistent instances of noncompliance” by the security agency but no “illegality or other abuse of authority” targeting domestic political activity.

Mr. Snowden’s disclosures are protected by the First Amendment, said Bruce Fein, a former Reagan administration lawyer who at one point represented Mr. Snowden's father. “It prohibits government from punishing communications that expose government lawlessness whether or not the illegality is classified,” he said. “Calling government to account for breaking the law is a compelling civic duty of all citizens.”

The amnesty idea won widespread attention last month when Richard Ledgett, who leads an N.S.A. task force evaluating damage from the disclosures, said on the CBS News program “60 Minutes” that it was “worth having a conversation about” it to prevent further revelations.

That position won further attention in the last week with editorials in The Guardian and The New York Times urging clemency. (The editorial page of The Times is run independently of the news department.) Debates about the idea played out on CNN, ABC and elsewhere, and Anne-Marie Slaughter, a former State Department official in the Obama administration, posted a message on Twitter in favor of clemency.

But inside the White House and the Justice Department, Mr. Ledgett’s suggestion has been met with stony opposition. The administration has made no move to reach out to negotiate any kind of deal and makes clear that it has no plans to. Officials express nothing but antipathy for Mr. Snowden, whose disclosures, one argued, have caused Al Qaeda and its allies “to change their tactics.”