Story highlights Two newspapers call for clemency for NSA leaker Edward Snowden

The Obama administration is against clemency

Leakers in the past have received some mercy

More recent cases show tougher consequences for their actions

Two prominent newspapers this week used their editorial pages to call for mercy for intelligence leaker Edward Snowden, with one arguing "he deserves better than a life of permanent exile, fear and flight."

The New York Times and The Guardian make the case for some sort of plea deal or clemency that would allow Snowden to return to the United States from Russia, where he was granted asylum.

Mercy or dropped charges have occurred in past cases of other high-profile whistle-blowers, such as Daniel Ellsberg, the military analyst behind the leak of the Pentagon Papers. But in recent years, the United States has aggressively pursued those who leak government secrets.

Here's a look at how the cases of five prominent leakers -- including Snowden -- have played out:

Daniel Ellsberg

Ellsberg was the military analyst who leaked the 7,000-page Pentagon Papers in 1971.

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Photos: Sharing secrets: U.S. intelligence leaks Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – John Walker ran a father and son spy ring, passing classified material to the Soviet Union from 1967 to 1985. Walker was a Navy communication specialist with financial difficulties when he walked into the Soviet Embassy and sold a piece of cyphering equipment. Navy and Defense officials said that Walker enabled the Soviet Union to unscramble military communications and pinpoint the location of U.S. submarines at all times. As part of his plea deal, prosecutors promised leniency for Walker's son Michael Walker, a former Navy seaman. Click through the gallery to see other high-profile leak scandals the United States has seen over the years. Hide Caption 1 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Military analyst Daniel Ellsberg leaked the 7,000-page Pentagon Papers in 1971. The top-secret documents revealed that senior American leaders, including three presidents, knew the Vietnam War was an unwinnable, tragic quagmire. Further, they showed that the government had lied to Congress and the public about the progress of the war. Ellsberg surrendered to authorities and was charged as a spy. During his trial, the court learned that President Richard Nixon's administration had embarked on a campaign to discredit Ellsberg, illegally wiretapping him and breaking into his psychiatrist's office. All charges against him were dropped. Since then he has lived a relatively quiet life as a respected author and lecturer. Hide Caption 2 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Jonathan Pollard is a divisive figure in U.S.-Israeli relations. The former U.S. Navy intelligence analyst was caught spying for Israel in 1985 and was sentenced in 1987 to life imprisonment. Previously, the United States and Israel discussed his possible release as part of efforts to save fragile Middle East peace negotiations, according to sources familiar with the talks. On July 28, 2015, Pollard's lawyer announced that the convicted spy had been granted parole and would be released on November 21 -- exactly 30 years after his arrest. Hide Caption 3 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Wen Ho Lee was a scientist at the Los Alamos Laboratory in New Mexico who was charged with 59 counts of downloading classified information onto computer tapes and passing it to China. Lee eventually agreed to plead guilty to a count of mishandling classified information after prosecutors deemed their case to be too weak. He was released after nine months in solitary confinement. Lee later received a $1.6 million in separate settlements with the government and five news agencies after he sued them, accusing the government of leaking damaging information about him to the media. Hide Caption 4 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Members of the Bush administration were accused retaliating against Valerie Plame, pictured, by blowing her cover in 2003 as a U.S. intelligence operative, after her husband, former Ambassador Joe Wilson, wrote a series of New York Times op-eds questioning the basis of certain facts the administration used to make the argument to go to war in Iraq. Hide Caption 5 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – In 2007, Lewis "Scooter" Libby, Vice President Dick Cheney's former chief of staff, was convicted on charges related to the leak of the identity of CIA operative Valerie Plame. Libby was convicted of obstruction of justice and perjury in connection with the case. His 30-month sentence was commuted by President George W. Bush. Cheney told a special prosecutor in 2004 that he had no idea who leaked the information. Hide Caption 6 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Aldrich Ames, a 31-year CIA employee, pleaded guilty to espionage charges in 1994 and was sentenced to life in prison. Ames was a CIA case worker who specialized in Soviet intelligence services and had been passing classified information to the KGB since 1985. U.S. intelligence officials believe that information passed along by Ames led to the arrest and execution of Russian officials they had recruited to spy for them. Hide Caption 7 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Robert Hanssen pleaded guilty to espionage charges in 2001 in return for the government not seeking the death penalty. Hanssen began spying for the Soviet Union in 1979, three years after going to work for the FBI and prosecutors said he collected $1.4 million for the information he turned over to the Cold War enemy. In 1981, Hanssen's wife caught him with classified documents and convinced him to stop spying, but he started passing secrets to the Soviets again four years later. In 1991, he broke off relations with the KGB, but resumed his espionage career in 1999, this time with the Russian Intelligence Service. He was arrested after making a drop in a Virginia park in 2001. Hide Caption 8 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Army Pvt. Bradley Manning was convicted July 30 of stealing and disseminating 750,000 pages of classified documents and videos to WikiLeaks, and the counts against him included violations of the Espionage Act. He was found guilty of 20 of the 22 charges but acquitted of the most serious charge -- aiding the enemy. Manning was sentenced to 35 years in military prison in 2013. Hide Caption 9 of 10 Photos: Sharing secrets: U.S. intelligence leaks Sharing secrets: U.S. intelligence leaks – Former intelligence contractor Edward Snowden revealed himself as the leaker of details of U.S. government surveillance programs run by the U.S. National Security Agency to track cell phone calls and monitor the e-mail and Internet traffic of virtually all Americans. Snowden has been granted temporary asylum in Russia after initially fleeing to Hong Kong. He has been charged with three felony counts, including violations of the U.S. Espionage Act, over the leaks. Hide Caption 10 of 10

Photos: Photos: NSA leaker Edward Snowden Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – National Security Agency leaker Edward Snowden poses with German Green party parliamentarian Hans-Christian Stroebele in Moscow on October 31. Stroebele returned from the meeting with a letter from Snowden to German authorities, which was distributed to the media. In it, Snowden said he is confident that with international support, the United States would abandon its efforts to "treat dissent as defection" and "criminalize political speech with felony charges." Hide Caption 1 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Snowden's refugee document granted by Russia is seen during a news conference in Moscow on August 1. Snowden slipped quietly out of the airport after securing temporary asylum in Russia , ending more than a month in limbo. Hide Caption 2 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Sen. Charles Schumer, D-New York, leaves a last-minute news conference at the U.S. Capitol after Russia announced that it would grant Snowden temporary asylum on August 1. "Russia has stabbed us in the back, and each day that Mr. Snowden is allowed to roam free is another twist of the knife," he said. Hide Caption 3 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Snowden's father, Lon Snowden, who has adamantly supported his son, talks to reporters in Washington on Tuesday, July 30. He has urged his son to remain in Russia "until we have assurances that he would receive a fair trial." Hide Caption 4 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Demonstrators in Berlin hold a protest march on Saturday, July 27, in support of Snowden and WikiLeaks document provider Bradley Manning. Both men have been portrayed as traitors and whistle-blowers. Manning was acquitted on July 30 on the most serious charge of aiding the enemy, but he was convicted on several other counts and likely faces a lengthy term in a military prison. Hide Caption 5 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Russian lawyer Anatoly Kucherena, center, speaks with journalists at the Sheremetyevo International Airport in Moscow after meeting with Snowden on Wednesday, July 24. Kucherena said he was in daily contact with Russian authorities about securing permission for Snowden to leave the airport. Hide Caption 6 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Snowden meets with human rights activists and lawyers on July 12 in a transit zone of the Russian airport. It was his first public appearance since he left Hong Kong on June 23. He announced that he was seeking refuge Russia while awaiting safe passage to Latin America, where he has been offered asylum. Hide Caption 7 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Russian President Vladimir Putin attends a meeting in Prokhorovka on July 12. Russian officials said Snowden abandoned his effort to seek asylum in the country after Putin warned that he would have to stop leaking information about U.S. surveillance programs if he wanted to stay. Hide Caption 8 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – A woman burns American flags during a protest in support of Bolivian President Evo Morales in front of the U.S. embassy in Mexico City on July 4. Leftist Latin American leaders and activists were fuming after some European nations temporarily refused Morales' plane access to their airspace amid suspicions Snowden was aboard. Hide Caption 9 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Bolivian President Evo Morales holds a news conference at the Vienna International Airport on July 3. He angrily denied any wrongdoing after his plane was diverted to Vienna and said that Bolivia is willing to give asylum to Snowden , as "fair protest" after four European countries restricted his plane from flying back from Moscow to La Paz. Hide Caption 10 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Umbrellas with slogans are lined up before a protest march to the U.S. consulate in Hong Kong on June 15. Snowden was hiding in Hong Kong, where he arrived on May 20 before blowing the lid off the NSA surveillance operation. Hide Caption 11 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Protesters in Hong Kong shout slogans in support of Snowden on June 13. The NSA leaker vowed to fight any bid to extradite him from Hong Kong. Hide Caption 12 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Graffiti sympathetic to Snowden is stenciled on the sidewalk in San Francisco on June 11. Hide Caption 13 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – An American flag flutters in front of the U.S. consulate in Hong Kong on June 10. Hide Caption 14 of 15 Photos: Photos: NSA leaker Edward Snowden NSA leaker Edward Snowden – Snowden outs himself on June 9 in the British newspaper The Guardian, which published details of his revelations about the NSA electronic surveillance programs. "I have no intention of hiding who I am because I know I have done nothing wrong," he said in a video interview. Hide Caption 15 of 15

The top-secret documents revealed that senior U.S. leaders, including three Presidents, knew the Vietnam War was an unwinnable, tragic quagmire. Further, they showed the government had lied to Congress and the public about the progress of the war.

Ellsberg surrendered to authorities and was charged as a spy.

During his trial, the court learned that President Richard Nixon's administration had embarked on a campaign to discredit Ellsberg, illegally wiretapping him and breaking into his psychiatrist's office. All charges against him were dropped. Since then, he has lived a relatively quiet life as a respected author and lecturer.

Chelsea Manning

U.S. Army Pvt. Chelsea Manning, who formerly went by the name Bradley , was convicted of stealing and disseminating 750,000 pages of classified documents and videos to WikiLeaks, the online anti-secrecy group.

A military judge sentenced Manning to 35 years -- far less than the effective life sentence that was permitted under law -- minus credit for about 3 1/2 years time served.

The judge also reduced Manning's rank, ordered that pay and benefits be forfeited, and imposed a dishonorable discharge.

Manning has applied for a pardon from President Barack Obama.

The Obama administration has said it will handle that request no differently than others. Manning's defenders, including Ellsberg, said he was a hero.

Julian Assange

Assange is the founder of WikiLeaks , which published hundreds of thousands of secret State Department cables and other information taken by Manning that gave the group global recognition.

Assange's case remains unresolved.

For more than a year, Assange has been holed up inside the Ecuadorian Embassy in London to avoid extradition to Sweden, where he is wanted for questioning over allegations that he raped one woman and sexually molested another.

Assange has repeatedly said the allegations in Sweden are politically motivated and tied to the work of his website. Ecuador's government granted him asylum, but British authorities have said they will arrest him if he leaves the premises.

Mark Felt

In 2005, retired deputy FBI director Felt revealed himself to be the whistle-blower "Deep Throat" in the Watergate scandal.

He anonymously assisted Washington Post reporters Carl Bernstein and Bob Woodward with many of their stories about the Nixon administration's cover-up after the June 1972 break-in at the Democratic National Committee headquarters.

The stories sparked a congressional investigation that eventually led to Nixon's resignation in 1974. The Post won a Pulitzer Prize for its coverage.

Felt was convicted on unrelated conspiracy charges in 1980 and fined. He was pardoned by President Ronald Reagan before slipping into obscurity for the next quarter century. He died in 2008 at age 95.

Edward Snowden

It's too early to tell Snowden's ultimate fate. A contentious debate surrounds his case

On one side, many see Snowden as a traitor and criminal for unlawfully taking and disseminating National Security Agency files relating to its mass collection of electronic information, including e-mail and phone data.

Others see bravery in Snowden's actions for bringing a secretive program to light and initiating a national debate about security and privacy.

"Considering the enormous value of the information he has revealed, and the abuses he has exposed, Mr. Snowden deserves better than a life of permanent exile, fear and flight," the Times editorial said. "He may have committed a crime to do so, but he has done his country a great service."

Still, U.S. officials have thus far shown no indication they're considering clemency.

Last month, Attorney General Eric Holder said the conversation about balance between security and privacy is important, "but I would not say what he did is worthy of clemency."

"It's not something that I would support," Holder said. "I think that he has clearly broken the law and harmed the nation that he claims to love."

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