President Obama has commuted more sentences than the last six presidents combined. Getty

With less than two weeks remaining in his eight-year administration, President Barack Obama will be under heavy pressure from public advocacy groups to grant high-profile pardon decisions. But Obama has not been shy about granting pardons and commuting prison sentences, particularly as a lame duck president.

Obama pardoned 78 people and commuted the sentences of 153 others Dec. 19, further cementing his legacy as the most generous grantor of clemency in modern presidential history.

The Department of Justice official website says Obama has granted 148 presidential pardons in his time in office, a number that exceeds the combined total of the last six presidents. In 2016, he pardoned 82 federal inmates, more than his seven previous years combined. Most of the pardons have been for drug offenders.

Obama waited until December 2010, to grant his first pardons, giving nine people clemency. He followed that with 13 in 2011, 30 in 2013, 12 in 2014 and two in 2015 for a total of 66 pardons in seven years.

He has also been generous with commuting sentences. Obama waited until November 2011, 34 months after taking office, to make his first commutation. It went to Eugenia Marie Jennings, a then-34-year-old Missouri woman who had served 10 years of a 22-year prison sentence for distributing crack cocaine. She had reportedly sold crack twice to support her three children, exchanging the drug for clothing. In 2011, Jennings was diagnosed with cancer and underwent chemotherapy.

Obama would make up for his relatively slow start, shortening the sentences of 1,177 people, of which 395 were life sentences. After Jennings in 2011, Obama waited until December 2013 to commute the sentences of eight other people. In 2014, Obama commuted 12 and later sharply increased the number to 163 for 2015. But 2016 saw the most pronounced surge, with Obama commuting 992 sentences, which included a one-day total of 214 on Aug. 3.

The acts of clemency have been part of Obama’s broad hopes to reduce the prison population, which has been burdened by what he described as “unjust and outdated prison sentences.”

“We need Congress to pass meaningful federal sentencing reform that will allow us to more effectively use taxpayer dollars to protect the public,” Obama wrote in a Facebook post Aug. 3.

Obama's commutations are in contrast to his predecessor. During George W. Bush's eight years in office, he granted only 11. In fact, the last five presidents combined commuted the sentences of just 117 people, less than a tenth of Obama's total so far.

But Obama has been less receptive to full pardons, and while he has outdone his predecessors, there are still tens of thousands of prisoners who have applied for clemency.

Obama has also been reluctant to pardon more renowned criminals, mostly limiting his list to little-known blue-collar offenders who carry what is perceived to be unnecessarily stiff sentences. It's possible that Obama may prefer to leave office quietly, having seen how previous presidents were vilified for their controversial pardons.

Gerald Ford pardoned predecessor Richard Nixon in September 1974, raising questions of an arranged deal. The action ultimately played a key role in Ford’s defeat in the 1976 election. In his final weeks in office, George H.W. Bush caused a stir when he pardoned former Defense Secretary Caspar Weinberger on Christmas Eve for his role in the Iran-Contra Scandal, which had taken place when Bush, a former CIA director, was vice-president. Hours before leaving office, Bill Clinton pardoned fugitive money man Marc Rich, who was married to a wealthy Democratic donor, prompting Clinton to explain his reasoning in a New York Times op-ed essay.

While Obama has shown leniency for drug offenders, it’s still somewhat unclear how he feels about those who have compromised national security. The big question ahead of Jan. 20 is whether Obama will grant clemency to famed NSA leaker Edward Snowden and Chelsea Manning, a former Army private and transgender woman who leaked military secrets to the website WikiLeaks in July 2013.

A full presidential pardon for either Snowden or Manning, or both, would be viewed as highly provocative despite strong appeals from notable organizations. Amnesty International and the American Civil Liberties Union, among many other human rights groups, have pushed for clemency for Snowden and Manning, and the two both have more than 100,000 signatures in separate petitions to the White House.

Manning, 29, may have a stronger chance for a pardon or commutation than Snowden. Serving a 35-year sentence, Manning has been imprisoned for more than six years, which is more than any whistleblower has served for providing information to a reporter. She has also been subjected to poor treatment in prison and attempted suicide twice, her lawyer has said.

There are other factors in play for Obama to potentially pardon Manning. She suffered from gender dysphoria while serving in Iraq, there have been no reprisals or deaths due to Manning’s leaks and she has sought contrition.

"I am not asking for a pardon of my conviction," Manning wrote in a letter to Obama in November. "I understand that the various collateral consequences of the court-martial conviction will stay on my record forever. The sole relief I am asking for is to be released from military prison after serving six years of confinement as a person who did not intend to harm the interests of the United States or harm any service members."

The case for Snowden is a bit more muddled. Snowden, who has gained celebrity status after a documentary and a recent film by Oliver Stone, had revealed the U.S. government collected telephone metadata, ultimately leading to corrective reform in November 2015. Former attorney general Eric Holder said the 33-year-old had done a “public service.”

But Snowden received temporary asylum in Russia, a country with a strained diplomatic relationship with the Obama administration, as he awaits permanent asylum. A House Intelligence Committee report concluded in December that while in Moscow, Snowden “had, and continues to have, contact with Russian intelligence services,” a revelation that comes after Russia reportedly hacked emails from the Democratic National Committee during a presidential election year. In short, Snowden didn’t do himself any favors by fleeing to China and then Russia.

But what may hurt Snowden the most is that he hasn’t stood trial. Obama provided a lengthy explanation on Snowden in an interview with German weekly magazine Der Spiegel in November.

“I can't pardon somebody who hasn't gone before a court and presented themselves, so that's not something that I would comment on at this point. I think that Mr. Snowden raised some legitimate concerns,” the president said. “How he did it was something that did not follow the procedures and practices of our intelligence community. If everybody took the approach that I make my own decisions about these issues, then it would be very hard to have an organized government or any kind of national security system.

“At the point at which Mr. Snowden wants to present himself before the legal authorities and make his arguments or have his lawyers make his arguments, then I think those issues come into play. Until that time, what I've tried to suggest — both to the American people, but also to the world — is that we do have to balance this issue of privacy and security. Those who pretend that there's no balance that has to be struck and think we can take a 100-percent absolutist approach to protecting privacy don't recognize that governments are going to be under an enormous burden to prevent the kinds of terrorist acts that not only harm individuals, but also can distort our society and our politics in very dangerous ways.

“And those who think that security is the only thing and don't care about privacy also have it wrong.”

If Obama were to pardon or commute Snowden or Manning, it may seem reasonable for him to do it hours or minutes before he leaves office. But in an interview with Politico last week, Mark Osler, a law professor at the University of St. Thomas in Minneapolis, cast doubt that Obama would make a bold last-minute pardon or commutation.

“I think he’s going to announce a lot of names in the next few weeks. I don’t think any of them will be these big-name figures,” he said. “This administration does have an aversion to high-profile cases generally.”