When it comes to executive clemency, Barack Obama is straight out of a Charles Dickens novel. He is the best of presidents and the worst of presidents. With his presidency in its final weeks, his record on leniency to those convicted of crimes is one that continues to puzzle.

Obama has long been critical of lengthy sentences imposed on drug offenders under laws that treated crimes involving crack cocaine more harshly than those involving powder cocaine. In 2010, he signed a law reducing the disparity. Changes in laws and Justice Department policies led to a huge drop in the number of drug offenders serving life sentences.

The 2010 change didn't apply to those already convicted. In 2014, though, the U.S. Sentencing Commission voted to cut sentences prescribed by its guidelines and made the change retroactive, abbreviating thousands of prison terms.

The president has focused his clemency powers on reducing sentences for federal inmates who meet certain conditions — such as earning general equivalency diplomas, participating in substance-abuse programs and having no gang ties or record of misconduct in prison.

Using that approach, he has been notably generous. In August, Obama commuted the sentences of 214 prisoners, including 67 serving life terms. On Nov. 4, he added 72, bringing his total to 944 felons, 324 of whom were in for life. "All of the individuals receiving commutation today, incarcerated under outdated and unduly harsh sentencing laws, embody the president's belief that 'America is a nation of second chances,' " White House counsel Neil Eggleston said in August.

P.S. Ruckman Jr., a political scientist at Rock Valley College in Rockford, Ill., says Obama's flurry of commutations "is the biggest fourth-year surge of any president in history." During his eight years, George W. Bush commuted the sentences of just 11 prisoners. Obama's total is more than double the number granted by all presidents from Lyndon Johnson through Bush combined.

So Obama is admirably merciful — or dangerously permissive, depending on your point of view — while Bush was the opposite? The picture is not so simple. Bush pardoned 189 people. Obama has granted only 70 pardons — "the lowest for any two-term president since George Washington," says Ruckman.

The discrepancy can't stem from an Obama fear that a pardoned felon will commit new crimes. Commutations, after all, grant inmates early release from prison. Pardons more often go to people already on the outside and trying to regain a place in society. Pardons restore civil rights, such as rights to vote, serve on juries and own guns, and make it easier to get occupational licenses and jobs.

Obama seems so intent on addressing the sentencing inequities and excesses of the 1990s that he has neglected other claims. It may not be entirely his fault. Margaret Colgate Love, who was the U.S. pardon attorney from 1990 to 1997, argues that the task of reviewing clemency petitions should be transferred out of the Justice Department for the simple reason that "federal prosecutors don't want to disturb cases that they have gone to a lot of trouble to convict," as she told Slate.

Presidential clemency is meant to be an instrument of wisdom and compassion. But Obama's use of it could be criticized as too generous, too harsh or both. If we can make our own plea as he weighs acts of clemency during his final days in office: A power this consequential should be employed in a way that is easier for the public to understand and accept.

FROM AN EDITORIAL IN THE CHICAGO TRIBUNE