President Donald Trump, like many of his predecessors, is likely to use his final days in the White House to increase his use of pardons and commutations, including some that may prove controversial.   Trump has already issued several politically charged clemencies, but the overall number of pardons and commutations he's granted to date pales in comparison to other presidents in the past century. The Constitution gives presidents the power of executive clemency for those convicted in federal criminal cases. Executive clemency has two main powers: Pardons overturn federal convictions, exempt people from punishment and restore various rights such as being allowed to vote, run for public office, hold professional licenses or own a gun. They do not erase the record of the conviction.  Commutations reduce sentences. Convictions remain intact. Pardons can't be used for state crimes or to save a president or other official from being impeached. Congress or courts can't overturn a pardon. The 29 people Trump has pardoned range from a women’s suffrage leader to servicemembers charged with murder to his ex-national security adviser who pleaded guilty to lying to the FBI: This year, Trump commuted the sentence of longtime confidant Roger Stone, a Republican operative convicted of lying to Congress to protect the president's campaign from the Russia investigation led by special counsel Robert Mueller. Trump has issued 15 others, too.  Pardons and commutations have actually been in decline during recent years — with exception of the hundreds of commutations granted by President Barack Obama for drug dealers who received mandatory-minimum sentences during the 1980s War on Drugs. In contrast, the number of requests for clemency have jumped in the past three decades. Obama received 36,544 in his eight years, and Trump has received nearly 11,000 during his term. While Trump trails recent presidents in the pardons and commutations granted, that doesn't take into account the possibility of 11th-hour clemencies. USA TODAY reported Trump is considering pardons that could be more controversial than those he has already granted, including those for close associates, family members and himself. No president has tried to pardon himself, so the legality of it has not been tested. Most legal experts, however, say it isn't possible. Could Trump pardon family members? His prior pardons may set the stage for more Can Trump pardon himself?: What's a preemptive pardon? Experts explain the sweeping power Should he be planning pardons for January — even his final morning in office on Jan. 20 — he would be in good company. Recent presidents have done the same, most notably Bill Clinton, who issued 141 pardons on his last day. George Washington The Whiskey Rebellion began in 1794 with a group of farmers and distillers from Pennsylvania. The group started violent protests over the federal government's ban on whiskey and other liquor. In the first act of federal clemency in American history, President George Washington pardoned the group to stop the violence. Andrew Johnson Pardoned all soldiers who fought for Confederacy. Above: Stone Mountain, a Confederate memorial in Georgia. Harry S. Truman Commuted sentence of Oscar Collazo, who was convicted of trying to assassinate Truman, from death to life imprisonment. In 1979, Jimmy Carter commuted Collazo’s life sentence, releasing him from prison. Above Collazo lies wounded at the base of the steps to Blair House, President Truman's temporary residence in Washington, D.C. Richard Nixon Commuted the sentence of former Teamster leader Jimmy Hoffa from 13 years in prison to time served of less than 5 years. Gerald Ford Pardoned Richard Nixon, a "full, free, and absolute pardon ... for all offenses against the United States which he has committed or may have committed or taken part in during the period from Jan. 20, 1969, through Aug. 9, 1974." Jimmy Carter Commuted sentence of Watergate burglar G. Gordon Liddy to 8 years from 20 years. Pardoned singer Peter Yarrow of Peter, Paul and Mary, who pleaded guilty in 1970 and served three months in jail after a relationship with a minor, a girl age 14. Pardoned 200,000 Vietnam War draft resisters. Commuted the seven-year sentence of Patty Hearst, who was kidnapped by the Symbionese Liberation Army in 1974 and later convicted of robbing a bank. Ronald Reagan Pardoned New York Yankees owner George Steinbrenner for making illegal contributions to Nixon's reelection campaign in 1972. George H.W. Bush Pardoned former Defense Secretary Caspar Weinberger, former national security adviser Robert McFarlane and four others for their involvement in Iran-Contra scandal. Bill Clinton Pardoned his half-brother, Roger Clinton, after his cocaine conviction in 1985.  Pardoned Patty Hearst. Pardoned financier Marc Rich, who was indicted on charges of nonpayment of $48 million in taxes and more than 50 counts of wire fraud and racketeering. He also was accused of violating a trade embargo with Iran. Rich stayed in Switzerland to avoid arrest. After the pardon, critics said Clinton was influenced by donations from Rich's ex-wife to the Democratic Party. Pardoned Susan McDougal, his former Whitewater business partner, and three others involved in an Arkansas real estate controversy. George W. Bush Commuted the sentence of I. Lewis "Scooter" Libby, chief of staff to Vice President Dick Cheney, who was found guilty of obstruction of justice, two counts of lying under oath, and making false statements in connection with the exposure of Valerie Plame Wilson as a CIA agent.  Barack Obama Commuted the 35-year sentence of former Army private Chelsea Manning, who was convicted of leaking classified information. Presidential pardons: Which president used their power the most? From Roger Stone to Chelsea Manning to Thanksgiving turkeys, here's all you need to know about presidential pardons and executive clemency. Just the FAQs, USA TODAY Contributing: Emily Johnson  SOURCE USA TODAY NETWORK reporting and research; U.S. Department of Justice; Cornell Law School; Gerald R. Ford Presidential Library; Pew Research Center Photos by USA TODAY, Getty Images, AP, Library of Congress