"The quality of mercy is not strain'd," wrote William Shakespeare in The Merchant of Venice. Obviously, the Bard never experienced pardon politics in the modern era.

The power of governors and presidents to pardon people or commute their sentences is nearly absolute. Even the most bitterly opposed pardons have no recourse, as those who attempted to reverse Bill Clinton's pardon of Marc Rich discovered. Some states offer constraining mechanisms before sentences can be pardoned or commuted — such as a requirement to consider recommendations from a panel — but once given the action is nearly unchallengeable. It is the purest exercise of executive power in the American model of government, and it intends to allow for recourse to common sense in rare instances of judicial injustice without any other remedy.

Yet pardoning at the presidential level has declined in the past few decades. ProPublica offered an enlightening chart in December 2011 for the previous 104 years, which bookends the golden age of presidential pardons between the FDR and LBJ administrations. The peak year for presidential clemency actions came in 1944, the last full year of Roosevelt's presidency, with 424 pardons. Johnson issued 364 in 1966.

In the nearly 50 years since, only three years have seen more than 200 pardons: two of them from Richard Nixon (235 in 1972 and 202 in 1973) and one from Clinton, who issued 218 pardons in a single month in 2001. Following the stink from the Rich pardon, federal prosecutors looked into potential corruption charges but came up empty. That didn't embolden George W. Bush to issue pardons; he didn't pardon anyone until 2003, and finished his presidency with 200 acts of clemency in eight years, less than half that of Clinton, although nearly three times as many as his father George H. W. Bush, who finished with 77 after four years.

If the quality of mercy is not strain'd, then the quantity certainly seems to be, and it hasn't improved much under Barack Obama — at least, not yet. In a little over five years, Obama has issued just 61 clemency actions, after spending his first two years in office ignoring thousands of petitions for either pardons or commutations. In 2013, the White House received 303 pardon requests and 2,370 requests for commutations, on top of the combined backlog of 3,058 applications. Obama granted a grand total of 17 pardons and no commutations that year.

Why has the U.S. presidency grown ever more cautious in exercising its comprehensive power of the pardon? In part, because the political backlash at state and federal levels has made pardons and commutations toxic. The Rich pardon was one of the most ugly examples, granted to a politically connected financier who fled the country rather than face tax-evasion charges.

But that's hardly the whole, sordid history of politically motivated pardons. Gerald Ford pardoned more than 400 people during his two-plus years as commander in chief, but his pardon of Nixon may have been the most politically damaging clemency action ever. Jimmy Carter issued a blanket pardon to Vietnam War draft dodgers. Ronald Reagan pardoned FBI agents who authorized illegal break-ins in the Nixon administration, and George H.W. Bush pardoned Reagan's aides implicated in the Iran-Contra affair. He also pardoned industrialist Armand Hammer for his illegal contributions to Nixon's campaign — just after Hammer kicked in more than $100,000 to the GOP.

Even well-intentioned clemency actions occasionally backfire. In 2008 and 2009, former Arkansas Gov. Mike Huckabee faced political attacks over commutations given to two prisoners who later went on to murder others. In one case, Huckabee argued with some justification that the action was enabled by his predecessor, but in the other he had no such defense.

Small wonder, then, that Obama has exercised caution. That may change, though, as Obama tries to establish a legacy on curtailing minimum sentencing in drug-related crimes. Yahoo's Liz Goodwin reports that Obama may be preparing to act soon to issue a significant number of pardons and commutations for those trapped in unjust mandatory-minimum sentences. Goodwin says "hundreds, perhaps thousands" of prisoners may find themselves freed by Obama over the final two-plus years of his presidency, which would challenge even FDR and LBJ's single-year records if it came to pass. The White House plans to streamline its clemency procedures, in part by replacing the Pardon Attorney Ronald Rogers, who is under fire for "mishandling a high-profile clemency petition."

This is long overdue. Congress passed mandatory-minimum sentencing over justified dissatisfaction with the judiciary for being too lenient. The problem, though, is that even the good intentions of these laws lead to obvious cases of injustice. Goodwin highlights one such case, that of Barbara Scrivner, who got 30 years without parole for taking part in a meth ring. Despite playing a minor role — her husband masterminded the ring — the judge had no choice but to hand down the 30-year sentence. That specific mandatory-minimum requirement has since been repealed, and prosecutors tell Goodwin that Scrivner probably wouldn't have gotten a 20-year sentence today — which is how long she's already served.

The near-absolute power of the pardon was meant for cases like Scrivner, and others trapped by excessive prosecution or sentencing. People who commit serious crimes should expect serious consequences, but justice requires that the punishment fit the crime. No system of justice is perfect, of course. When the judicial process fails to deliver a just outcome, governors and presidents should exercise their authority to correct the excesses, while employing a competent screening process to assure that cases of true injustice receive clemency, rather than those that are mere favors for those with political connections.

Shakespeare's Portia wasn't quite finished with the quality of mercy. "It is twice blest," she explains, "it blesseth him that gives and him that takes." Perhaps we will see presidents and governors absorb that wisdom and offer a greater number of prudent exercises of executive clemency, choosing mercy and courage over political safety.