In the modern era, the pardon process is dominated by the Department of Justice, which issues a recommendation to the president. According to Morison, that recommendation is the only information the president sees nearly 100 percent of the time.
Trump has taken a different tack in deciding who should be pardoned.
Rather than relying on the Justice Department for recommendations on who should be pardoned, Trump has chosen to pardon individuals he knows personally or has seen on television.
In his Thursday announcement that he would pardon D'Souza, the president said he knew D'Souza because of reading about him in newspapers and seeing him on television.
Both Stewart and Blagojevich are connected to the president's television show, NBC's "The Celebrity Apprentice." Blagojevich appeared on Trump's show in the spring of 2010, and Stewart hosted a spinoff, called the "The Apprentice: Martha Stewart."
In his most provocative — and first — pardon, Trump granted clemency to Joe Arpaio, the controversial former sheriff of Maricopa County, Ariz., who gained celebrity as an early Trump supporter who occasionally spoke at the president's rallies.
Other aspects beyond a tug-of-war with the Justice Department may be involved in Trump's pardoning decisions, such as personal vendettas. Take the case of Scooter Libby as an example.
In April, Trump pardoned Libby, who was convicted in 2007 of lying to the FBI while serving as Vice President Dick Cheney's chief of staff. The special counsel who prosecuted the Libby case, Patrick Fitzgerald, was appointed by none other than James Comey.
Trump fired Comey as FBI director after clashing with him amid the Russia investigation and has called him a liar and an "untruthful slimeball." On the same day that Trump pardoned Libby, he seemed to refer to Comey as well as former FBI deputy director Andrew McCabe as a "den of thieves and lowlifes."
The D'Souza pardon, meanwhile, appears to be a stick in the eye for former U.S. Attorney Preet Bharara, who was fired along with 46 other attorneys appointed by President Barack Obama and has since become a public foil to the president.
And notably, Comey prosecuted Stewart while Fitzgerald oversaw the prosecution of Blagojevich.